Subjects: Biology >> Botany >> Plant biochemistry, plant Biophysics submitted time 2016-05-03
Abstract： OsNRT1.1a is a low-affinity nitrate (NO3 ) transporter gene. In this study, another mRNA splicing product, OsNRT1.1b, putatively encoding a protein with six transmembrane domains, was identified based on the rice genomic database and bioinformatics analysis. OsNRT1.1a/OsNRT1.1b expression in Xenopus oocytes showed OsNRT1.1a-expressing oocytes accumulated 15N levels to about half as compared to OsNRT1.1b-expressing oocytes. The electrophysiological recording of OsNRT1.1b-expressing oocytes treated with 0.25mM NO3 confirmed 15N accumulation data. More functional assays were performed to examine the function of OsNRT1.1b in rice. The expression of both OsNRT1.1a and OsNRT1.1b was abundant in roots and downregulated by nitrogen (N) deficiency. The shoot biomass of transgenic rice plants with OsNRT1.1a or OsNRT1.1b overexpression increased under various N supplies under hydroponic conditions compared to wild-type (WT). The OsNRT1.1a overexpression lines showed increased plant N accumulation compared to the WT in 1.25mM NH4NO3 and 2.5mM NO3 – or NH4 þ treatments, but not in 0.125mMNH4NO3. However, OsNRT1.1b overexpression lines increased total N accumulation in all N treatments, including 0.125mM NH4NO3, suggesting that under low N condition, OsNRT1.1b would accumulate more N in plants and improve rice growth, but also that OsNRT1.1a had no such function in rice plants.(NO3−) transporter gene. In this study, another mRNA splicing product, OsNRT1.1b, putatively encoding a protein with six transmembrane domains, was identified based on the rice genomic database and bioinformatics analysis. OsNRT1.1a/OsNRT1.1b expression in Xenopus oocytes showed OsNRT1.1a-expressing oocytes accumulated 15N levels to about half as compared to OsNRT1.1b-expressing oocytes. The electrophysiological recording of OsNRT1.1b-expressing oocytes treated with 0.25 mM NO3− confirmed 15N accumulation data. More functional assays were performed to examine the function of OsNRT1.1b in rice. The expression of both OsNRT1.1a and OsNRT1.1b was abundant in roots and downregulated by nitrogen (N) deficiency. The shoot biomass of transgenic rice plants with OsNRT1.1a or OsNRT1.1b overexpression increased under various N supplies under hydroponic conditions compared to wild-type (WT). The OsNRT1.1a overexpression lines showed increased plant N accumulation compared to the WT in 1.25 mM NH4NO3 and 2.5 mM NO3– or NH4+ treatments, but not in 0.125 mM NH4NO3. However, OsNRT1.1b overexpression lines increased total N accumulation in all N treatments, including 0.125 mM NH4NO3, suggesting that under low N condition, OsNRT1.1b would accumulate more N in plants and improve rice growth, but also that OsNRT1.1a had no such function in rice plants.
Peer Review Status:
Awaiting Review
Subjects: Biology >> Botany >> Plant cytology, plant genetics & plant morphology submitted time 2016-05-03
Abstract： Due to the remarkable adaptability to various environments, rice varieties with diverse flowering times have been domesticated or improved from Oryza rufipogon. Detailed knowledge of the genetic factors controlling flowering time will facilitate understanding the adaptation mechanism in cultivated rice and enable breeders to design appropriate genotypes for distinct preferences. In this study, four genes (Hd1, DTH8, Ghd7 and OsPRR37) in a rice long-day suppression pathway were collected and sequenced in 154, 74, 69 and 62 varieties of cultivated rice (Oryza sativa) respectively. Under long-day conditions, varieties with nonfunctional alleles flowered significantly earlier than those with functional alleles. However, the four genes have different genetic effects in the regulation of flowering time: Hd1 and OsPRR37 are major genes that generally regulate rice flowering time for all varieties, while DTH8 and Ghd7 only regulate regional rice varieties. Geographic analysis and network studies suggested that the nonfunctional alleles of these suppression loci with regional adaptability were derived recently and independently. Alleles with regional adaptability should be taken into consideration for genetic improvement. The rich genetic variations in these four genes, which adapt rice to different environments, provide the flexibility needed for breeding rice varieties with diverse flowering times.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Plant cytology, plant genetics & plant morphology submitted time 2016-05-03
Yan Zou
Satya Chintamanani
Ping He
Hirotada Fukushige
Liping Yu
Meiyu Shao
Lihuang Zhu
David F. Hildebrand
Xiaoyan Tang
Jian-Min Zhou
Abstract： Jasmonates (JAs) are rapidly induced after wounding and act as key regulators for wound induced signaling pathway. However, what perceives the wound signal and how that triggers JA biosynthesis remains poorly understood. To identify components involved in Arabidopsis wound and JA signaling pathway, we screened for mutants with abnormal expression of a luciferase reporter, which is under the control of a wound-responsive promoter of an ethylene response factor (ERF) transcription factor gene, RAP2.6 (Related to APetala 2.6). The rea1 (R
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Botany research, experiment, plant evolution & development submitted time 2016-05-03
Abstract： Production of β-ketoacyl-CoA, which is catalyzed by 3-ketoacyl-CoA synthase (KCS), is the first step in very long chain fatty acid (VLCFA) biosynthesis. Here we identified 58 KCS genes from Gossypium hirsutum, 31 from G. arboreum and 33 from G. raimondii by searching the assembled cotton genomes. The gene family was divided into the plant-specific FAE1-type and the more general ELO-type. KCS transcripts were widely expressed and 32 of them showed distinct subgenome-specific expressions in one or more cotton tissues/organs studied. Six GhKCS genes rescued the lethality of elo2Δelo3Δ yeast double mutant, indicating that this gene family possesses diversified functions. Most KCS genes with GA-responsive elements (GAREs) in the promoters were significantly upregulated by gibberellin A3 (GA). Exogenous GA3 not only promoted fiber length, but also increased the thickness of cell walls significantly. GAREs present also in the promoters of several cellulose synthase (CesA) genes required for cell wall biosynthesis and they were all induced significantly by GA3. Because GA treatment resulted in longer cotton fibers with thicker cell walls and higher dry weight per unit cell length, we suggest that it may regulate fiber elongation upstream of the VLCFA-ethylene pathway and also in the downstream steps towards cell wall synthesis.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Plant biochemistry, plant Biophysics submitted time 2016-05-03
Jinfeng Qi
Jiancai Li
Xiu Han
Ran Li
Jianqiang Wu
Haixin Yu
Lingfei Hu
Yutao Xiao
Jing Lu
Yonggen Lou
Abstract：
Jasmonic acid (JA) and related metabolites play a key role in plant defense and growth. JA carboxyl methyltransferase (JMT) may be involved in plant defense and development by methylating JA to methyl jasmonate (MeJA) and thus influencing the concentrations of JA and related metabolites. However, no JMT gene has been well characterized in monocotyledon defense and development at the molecular level. After we cloned a rice JMT gene, OsJMT1, whose encoding protein was localized in the cytosol, we found that the recombinant OsJMT1 protein catalyzed JA to MeJA. OsJMT1 is up-regulated in response to infestation with the brown planthopper (BPH; Nilaparvata lugens). Plants in which OsJMT1 had been overexpressed (oe-JMT plants) showed reduced height and yield. These oe-JMT plants also exhibited increased MeJA levels but reduced levels of herbivore-induced JA and jasmonoyl-isoleucine (JA-Ile). The oe-JMT plants were more attractive to BPH female adults but showed increased resistance to BPH nymphs, probably owing to the different responses of BPH female adults and nymphs to the changes in levels of H2O2 and MeJA in oe-JMT plants. These results indicate that OsJMT1, by altering levels of JA and related metabolites, plays a role in regulating plant development and herbivore-induced defense responses in rice.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Botany research, experiment, plant evolution & development submitted time 2016-05-03
Abstract： Plants have evolved a large number of transcription factors (TF), which are enriched among duplicate genes, highlighting their roles in complex regulatory networks. The APETALA2/EREBP-like genes constitute a large plant TF family and participate in development and stress responses. To probe the conservation and divergence of AP2/EREBP genes, we analyzed the duplication patterns of this family in Brassicaceae and identified interacting proteins of representative Arabidopsis AP2/EREBP proteins. We found that many AP2/EREBP duplicates generated early in Brassicaceae history were quickly lost, but many others were retained in all tested Brassicaceae species, suggesting early functional divergence followed by persistent conservation. In addition, the sequences of the AP2 domain and exon numbers were highly conserved in rosids. Furthermore, we used 16 A. thaliana AP2/EREBP proteins as baits in yeast screens and identified 1,970 potential AP2/EREBP-interacting proteins, with a small subset of interactions verified in planta. Many AP2 genes also exhibit reduced expression in an anther-defective mutant, providing a possible link to developmental regulation. The putative AP2-interacting proteins participate in many functions in development and stress responses, including photomorphogenesis, flower development, pathogenesis, drought and cold responses, abscisic acid and auxin signaling. Our results present the AP2/EREBP evolution patterns in Brassicaceae, and support a proposed interaction network of AP2/EREBP proteins and their putative interacting proteins for further study.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Plant cytology, plant genetics & plant morphology submitted time 2016-05-03
Abstract：
Rice caryopsis as one of the most important food sources for humans has a complex structure that is composed of maternal tissues including the pericarp and testa and filial tissues including the endosperm and embryo. Although rice caryopsis studies have been conducted previously, a systematic characterization throughout the entire developmental process is still lacking. In this study, detailed morphological examinations of caryopses were made during the entire 30-day developmental process. We observed some rapid changes in cell differentiation events and cataloged how cellular degeneration processes occurred in maternal tissues. The differentiations of tube cells and cross cells were achieved by 9 days after pollination (DAP). In the testa, the outer integument was degenerated by 3 DAP, while the outer layer of the inner integument degenerated by 7 DAP. In the nucellus, all tissues with the exception of the nucellar projection and the nucellar epidermis degenerated in the first 5 DAP. By 21 DAP, all maternal tissues, including vascular bundles, the nucellar projection and the nucellar epidermal cells were degenerated. In summary, this study provides a complete atlas of the dynamic changes in cell differentiation and degeneration for individual maternal cell layers of rice caryopsis.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Plant biochemistry, plant Biophysics submitted time 2016-05-03
Abstract：
As a ubiquitous reaction, glucosylation controls the bioactivity of cytokinins in plant growth and development. Here we show that genetic manipulation of zeatin-O-glucosylation regulates the formation of important agronomic traits in rice by manipulating the expression of OscZOG1 gene, encoding a putative zeatin O-glucosyltransferase. We found that OscZOG1 was preferentially expressed in shoot and root meristematic tissues and nascent organs. The growth of lateral roots was stimulated in the overexpression lines, but inhibited in RNA interference lines. In shoots, knockdown of OscZOG1 expression by RNA interference significantly improved tillering, panicle branching, grain number per panicle and seed size, which are important agronomic traits for grain yield. In contrast, constitutive expression of OscZOG1 leads to negative effects on the formation of the grain-yielding traits with a marked increase in the accumulation levels of cis-zeatin O-glucoside (cZOG) in the transgenic rice plants. In this study, our findings demonstrate the feasibility of improving the critical yield-determinant agronomic traits, including tiller number, panicle branches, total grain number per panicle and grain weight by downregulating the expression level of OscZOG1. Our results suggest that modulating the levels of cytokinin glucosylation can function as a fine-tuning switch in regulating the formation of agronomic traits in rice.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Plant physiology submitted time 2016-05-03
Abstract：
In Arabidopsis, the phytohormone abscisic acid (ABA) plays a vital role in inhibiting seed germination and in post-germination seedling establishment. In the ABA signaling pathway, ABI5, a basic Leu zipper transcription factor, has important functions in the regulation of seed germination. ABI5 protein localizes in nuclear bodies, along with AFP, COP1, and SIZ1, and was degraded through the 26S proteasome pathway. However, the mechanisms of ABI5 nuclear body formation and ABI5 protein degradation remain obscure. In this study, we found that the Arabidopsis CROWDED NUCLEI (CRWN) proteins, predicted nuclear matrix proteins essential for maintenance of nuclear morphology, also participate in ABA-controlled seed germination by regulating the degradation of ABI5 protein. During seed germination, the crwn mutants are hypersensitive to ABA and have higher levels of ABI5 protein compared to wild type. Genetic analysis suggested that CRWNs act upstream of ABI5. The observation that CRWN3 colocalizes with ABI5 in nuclear bodies indicates that CRWNs might participate in ABI5 protein degradation in nuclear bodies. Moreover, we revealed that the extreme C-terminal of CRWN3 protein is necessary for its function in the response to ABA in germination. Our results suggested important roles of CRWNs in ABI5 nuclear body organization and ABI5 protein degradation during seed germination.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Plant biochemistry, plant Biophysics submitted time 2016-05-03
Abstract： >Flowering is a highly orchestrated and extremely critical process in a plant's life cycle. Previous study has demonstrated that SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) and FLOWERING LOCUS T (FT) integrate the gibberellic acid (GA) signaling pathway and vernalization pathway in regulating flowering time, but detailed molecular mechanisms remain largely unclear. In GA signaling pathway, DELLA proteins are a group of master transcriptional regulators, while in vernalization pathway FLOWERING LOCUS C (FLC) is a core transcriptional repressor that down-regulates the expression of SOC1 and FT. Here, we report that DELLA proteins interact with FLC in vitro and in vivo, and the LHRI domains of DELLAs and the C-terminus of MADS domain of FLC are required for these interactions. Phenotypic and gene expression analysis showed that mutation of FLC reduces while over-expression of FLC enhances the GA response in the flowering process. Further, DELLA-FLC interactions promote the repression ability of FLC on its target genes. In summary, these findings report that the interaction between MADS box transcription factor FLC and GRAS domain regulator DELLAs may integrate various signaling inputs in flowering time control, and shed new light on the regulatory mechanism both for FLC and DELLAs in regulating gene expression.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Plant biochemistry, plant Biophysics submitted time 2016-05-03
Yingni Xiao
Shawn Thatcher
Min Wang
Tingting Wang
Mary Beatty
Gina Zastrow-Hayes
Lin Li
Jiansheng Li
Bailin Li and Xiaohong Yang
Abstract：
Starch is the major component in maize kernels, providing a stable carbohydrate source for humans and livestock as well as raw material for the biofuel industry. Increasing maize kernel starch content will help meet industry demands and has the potential to increase overall yields. We developed a pair of maize near-isogenic lines (NILs) with different alleles for a starch quantitative trait locus on chromosome 3 (qHS3), resulting in different kernel starch content. To investigate the candidate genes for qHS3 and elucidate their effects on starch metabolism, RNA-Seq was performed for the developing kernels of the NILs at 14 and 21 d after pollination (DAP). Analysis of genomic and transcriptomic data identified 76 genes with nonsynonymous single nucleotide polymorphisms and 384 differentially expressed genes (DEGs) in the introgressed fragment, including a hexokinase gene, ZmHXK3a, which catalyzes the conversion of glucose to glucose-6-phosphate and may play a key role in starch metabolism. The expression pattern of all DEGs in starch metabolism shows that altered expression of the candidate genes for qHS3 promoted starch synthesis, with positive consequences for kernel starch content. These results expand the current understanding of starch biosynthesis and accumulation in maize kernels and provide potential candidate genes to increase starch content.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Plant biochemistry, plant Biophysics submitted time 2016-05-03
Maria Elisa Sabatini
Mattia Donà
Paola Leonetti
Andrea Minio
Massimo Delledonne
Daniela Carbonera
Massimo Confalonieri
Giorgio Giraffa and Alma Balestrazzi
Abstract：
The role of plant tyrosyl-DNA phosphodiesterase 1α in genome stability is studied using a Medicago truncatula MtTdp1α-depleted line. Lack of MtTdp1α results in a 39% reduction of methylated cytosines as compared to control. RNA-Seq analyses revealed that 11 DNA transposons and 22 retrotransposons were differentially expressed in the Tdp1α-2a line. Among them all, DNA transposons (MuDR, hAT, DNA3-11_Mad) and seven retrotransposons (LTR (Long Terminal Repeat)/Gipsy, LTR/Copia, LTR and NonLTR/L1) were down-regulated, while the 15 retrotransposons were up-regulated. Results suggest that the occurrence of stress-responsive cis-elements as well as changes in the methylation pattern at the LTR promoters might be responsible for the enhanced retrotransposon transcription.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Plant physiology submitted time 2016-05-03
Jasmin Herden
Stefan Meldau
Sang-Gyu Kim
Grit Kunert
Youngsung Joo
Ian T. Baldwin and Meredith C. Schuman
Abstract：
Arabidopsis thaliana plants are less resistant to attack by the generalist lepidopteran herbivore Trichoplusia ni when plants and herbivores are entrained to opposite, versus identical diurnal cycles and tested under constant conditions. This effect is associated with circadian fluctuations in levels of jasmonic acid, the transcription factor MYC2, and glucosinolate contents in leaves. We tested whether a similar effect could be observed in a different plant-herbivore system: the wild tobacco Nicotiana attenuata and its co-evolved specialist herbivore, Manduca sexta. We measured larval growth on plants under both constant and diurnal conditions following identical or opposite entrainment, profiled the metabolome of attacked leaf tissue, quantified specific metabolites known to reduce M. sexta growth, and monitored M. sexta feeding activity under all experimental conditions. Entrainment did not consistently affect M. sexta growth or plant defense induction. However, both were reduced under constant dark conditions, as was M. sexta feeding activity. Our data indicate that the response induced by M. sexta in N. attenuata is robust to diurnal cues and independent of plant or herbivore entrainment. We propose that while the patterns of constitutive or general damage-induced defense may undergo circadian fluctuation, the orchestration of specific induced responses is more complex.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Plant physiology submitted time 2016-05-03
Abstract：
In flowering plants, pollen tube growth is essential for delivery of male gametes into the female gametophyte or embryo sac for double fertilization. Although many genes have been identified as being involved in the process, the molecular mechanisms of pollen tube growth remains poorly understood. In this study, we identified that the Arabidopsis Transmembrane Protein 18 (AtTMEM18) gene played important roles in pollen tube growth. The AtTMEM18 shares a high similarity with the Transmembrane 18 proteins (TMEM18s) that are conserved in most eukaryotes and may play important roles in obesity in humans. Mutation in the AtTMEM18 by a Ds insertion caused abnormal callose deposition in the pollen grains and had a significant impact on pollen germination and pollen tube growth. AtTMEM18 is expressed in pollen grains, pollen tubes, root tips and other vegetative tissues. The pollen-rescued assays showed that the mutation in AtTMEM18 also caused defects in roots, stems, leaves and transmitting tracts. AtTMEM18-GFP was located around the nuclei. Genetic assays demonstrated that the localization of AtTMEM18 around the nuclei in the generative cells of pollen grains was essential for the male fertility. Furthermore, expression of the rice TMEM18-homologous protein (OsTMEM18) driven by LAT52 promoter could recover the fertility of the Arabidopsis attmem18 mutant. These results suggested that the TMEM18 is important for plant growth in Arabidopsis.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Botany research, experiment, plant evolution & development submitted time 2016-05-03
Abstract：
The evolution of long corolla tubes has been hypothesized to be driven by long-tongued pollinators. Corolla tubes in Pedicularis species can be longer than 10 cm which may function as flower stalks to increase visual attractiveness to pollinators because these species provide no nectar and are pollinated by bumblebees. The corolla tube length was manipulated (shorter or longer) in two Pedicularis species in field to examine whether longer tubes are more attractive to pollinators and produce more seeds than short tubes. Our results did not support the pollinator attraction hypothesis, leaving the evolution of long tubes in Pedicularis remains mysterious.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Plant physiology submitted time 2016-05-03
Lichao Zhang
Guoxiang Liu
Jizeng Jia
Guangyao Zhao
Chuan Xia
Lina Zhang
Fu Li
Qiang Zhang
Chunhao Dong
Shuangcheng Gao
Longzhi Han
Xiuping Guo
Xin Zhang
Jinxia Wu
Xu Liu
Xiuying Kong
Abstract： >Through large-scale transformation analyses, TaMYB72 was identified as a flowering time regulator in wheat. TaMYB72 is a MYB family transcription factor localized to the nucleus. Three TaMYB72 homologs, TaMYB72-A, TaMYB72-B and TaMYB72-D, cloned from hexaploid wheat were mapped to the short arm of the group 6 chromosomes. Under the long-day conditions, over-expression of the TaMYB72 in rice shortened the flowering time by approximately 12 d. Expression analyses suggest that TaMYB72 may function through up-regulation of florigen genes Hd3a and RFT1.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Plant physiology submitted time 2016-05-03
Abstract：
In plants, Vacuole H+-PPases (VPPs) are important proton pumps and encoded by multiple genes. In addition to full-length VPPs, several truncated forms are expressed, but their biological functions are unknown. In this study, we functionally characterized maize vacuole H+-PPase 5 (ZmVPP5), a truncated VPP in the maize genome. Although ZmVPP5 shares high sequence similarity with ZmVPP1, ZmVPP5 lacks the complete structure of the conserved proton transport and the inorganic pyrophosphatase-related domain. Phylogenetic analysis suggests that ZmVPP5 might be derived from an incomplete gene duplication event. ZmVPP5 is expressed in multiple tissues, and ZmVPP5 was detected in the plasma membrane, vacuole membrane and nuclei of maize cells. The overexpression of ZmVPP5 in yeast cells caused a hypersensitivity to salt stress. Transgenic maize lines with overexpressed ZmVPP5 also exhibited the salt hypersensitivity phenotype. A yeast two-hybrid analysis identified the ZmBag6-like protein as a putative ZmVPP5-interacting protein. The results of bimolecular luminescence complementation (BiLC) assay suggest an interaction between ZmBag6-like protein and ZmVPP5 in vivo. Overall, this study suggests that ZmVPP5 might act as a VPP antagonist and participate in the cellular response to salt stress. Our study of ZmVPP5 has expanded the understanding of the origin and functions of truncated forms of plant VPPs.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Plant physiology submitted time 2016-05-03
Yugo Lima-Melo
Fabricio E. L. Carvalho
Má
rcio O. Martins
Gisele Passaia
Rachel H. V. Sousa
Milton C. Lima Neto
Má
rcia Margis-Pinheiro
Joaquim A. G. Silveira
Abstract：
The physiological role of plant mitochondrial glutathione peroxidases is scarcely known. This study attempted to elucidate the role of a rice mitochondrial isoform (GPX1) in photosynthesis under normal growth and salinity conditions. GPX1 knockdown rice lines (GPX1s) were tested in absence and presence of 100 mM NaCl for 6 d. Growth reduction of GPX1s line under non-stressful conditions, compared with non-transformed (NT) plants occurred in parallel to increased H2O2 and decreased GSH contents. These changes occurred concurrently with photosynthesis impairment, particularly in Calvin cycle's reactions, since photochemical efficiency did not change. Thus, GPX1 silencing and downstream molecular/metabolic changes modulated photosynthesis differentially. In contrast, salinity induced reduction in both phases of photosynthesis, which were more impaired in silenced plants. These changes were associated with root morphology alterations but not shoot growth. Both studied lines displayed increased GPX activity but H2O2 content did not change in response to salinity. Transformed plants exhibited lower photorespiration, water use efficiency and root growth, indicating that GPX1 could be important to salt tolerance. Growth reduction of GPX1s line might be related to photosynthesis impairment, which in turn could have involved a cross talk mechanism between mitochondria and chloroplast originated from redox changes due to GPX1 deficiency.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Plant physiology submitted time 2016-05-03
Abstract：
Leaf senescence is the final leaf developmental process that is regulated by both intracellular factors and environmental conditions. The mitogen-activated protein kinase (MAPK) signaling cascades have been shown to play important roles in regulating leaf senescence; however, the component(s) downstream of the MAPK cascades in regulating leaf senescence are not fully understood. Here we showed that the transcriptions of ZmMEK1, ZmSIMK1, and ZmMPK3 were induced during dark-induced maize leaf senescence. Furthermore, in-gel kinase analysis revealed the 42 kDa MAPK was activated. ZmMEK1 interacted with ZmSIMK1 in yeast and maize mesophyll protoplasts and ZmSIMK1 was activated by ZmMEK1 in vitro. Expression of a dominant negative mutant of ZmMEK1 in Arabidopsis transgenic plants induced salicylic acid (SA) accumulation and SA-dependent leaf senescence. ZmMEK1 interacted with Arabidopsis MPK4 in yeast and activated MPK4 in vitro. SA treatment accelerated dark-induced maize leaf senescence. Moreover, blockage of MAPK signaling increased endogenous SA accumulation in maize leaves. These findings suggest that ZmMEK1-ZmSIMK1 cascade and its modulating SA levels play important roles in regulating leaf senescence.
Peer Review Status:Awaiting Review
Subjects: Biology >> Botany >> Plant biochemistry, plant Biophysics submitted time 2016-05-03
Gaojie Ji
Jie Zhang
Haiying Zhang
Honghe Sun
Guoyi Gong
Jianting Shi
Shouwei Tian
Shaogui Guo
Yi Ren
Huolin Shen
Junping Gao
Yong Xu
Abstract：
Although it has been reported previously that ethylene plays a critical role in sex determination in cucurbit species, how the andromonoecy that carries both the male and hermaphroditic flowers is determined in watermelon is still unknown. Here we showed that the watermelon gene 1-aminocyclopropane-1-carboxylate synthase 4 (CitACS4), expressed specifically in carpel primordia, determines the andromonoecy in watermelon. Among four single nucleotide polymorphism (SNPs) and one InDel identified in the coding region of CitACS4, the C364W mutation located in the conserved box 6 was co-segregated with andromonoecy. Enzymatic analyses showed that the C364W mutation caused a reduced activity in CitACS4. We believe that the reduced CitACS4 activity may hamper the programmed cell death in stamen primordia, leading to the formation of hermaphroditic flowers.
Peer Review Status:Awaiting Review
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