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Genetic and Physio-Biochemical Characterization of a Novel Premature Senescence Leaf Mutant in Rice (Oryza sativa L.).

ABSTRACT: Premature senescence greatly affects the yield production and the grain quality in plants, although the molecular mechanisms are largely unknown. Here, we identified a novel rice premature senescence leaf 85 (psl85) mutant from ethyl methane sulfonate (EMS) mutagenesis of cultivar Zhongjian100 (the wild-type, WT). The psl85 mutant presented a distinct dwarfism and premature senescence leaf phenotype, starting from the seedling stage to the mature stage, with decreasing level of chlorophyll and degradation of chloroplast, declined photosynthetic capacity, increased content of malonaldehyde (MDA), upregulated expression of senescence-associated genes, and disrupted reactive oxygen species (ROS) scavenging system. Moreover, endogenous abscisic acid (ABA) level was significantly increased in psl85 at the late aging phase, and the detached leaves of psl85 showed more rapid chlorophyll deterioration than that of WT under ABA treatment, indicating that PSL85 was involved in ABA-induced leaf senescence. Genetic analysis revealed that the premature senescence leaf phenotype was controlled by a single recessive nuclear gene which was finally mapped in a 47 kb region on the short arm of chromosome 7, covering eight candidate open reading frames (ORFs). No similar genes controlling a premature senescence leaf phenotype have been identified in the region, and cloning and functional analysis of the gene is currently underway.

SUBMITTER: He Y

PROVIDER: S-EPMC6122088 | biostudies-other | 2018 Aug

REPOSITORIES: biostudies-other

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Genetic and Physio-Biochemical Characterization of a Novel Premature Senescence Leaf Mutant in Rice (Oryza sativa L.).

He Yan Y Zhang Zhihong Z Li Liangjian L Tang Shaoqing S Wu Jian-Li JL

International journal of molecular sciences 20180809 8

Premature senescence greatly affects the yield production and the grain quality in plants, although the molecular mechanisms are largely unknown. Here, we identified a novel rice premature senescence leaf 85 (psl85) mutant from ethyl methane sulfonate (EMS) mutagenesis of cultivar Zhongjian100 (the wild-type, WT). The psl85 mutant presented a distinct dwarfism and premature senescence leaf phenotype, starting from the seedling stage to the mature stage, with decreasing level ...[more]

PMID: 30096885

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Project description:BackgroundIncreased water and labour scarcity in major rice growing areas warrants a shift towards direct seeded rice cultivation under which management of weeds is a major issue. Use of broad spectrum non-selective herbicides is an efficient means to manage weeds. Availability of rice genotypes with complete tolerance against broad-spectrum non-selective herbicides is a pre-requisite for advocating use of such herbicides. In the present study, we developed an EMS induced rice mutant, 'HTM-N22', exhibiting tolerance to a broad spectrum herbicide, 'Imazethapyr', and identified the mutations imparting tolerance to the herbicide.ResultsWe identified a stable and true breeding rice mutant, HTM-N22 (HTM), tolerant to herbicide, Imazethapyr, from an EMS-mutagenized population of approximately 100,000 M2 plants of an upland rice variety, Nagina 22 (N22). Analysis of inheritance of herbicide tolerance in a cross between Pusa 1656-10-61/HTM showed that this trait is governed by a single dominant gene. To identify the causal gene for Imazethapyr tolerance, bulked segregant analysis (BSA) was followed using microsatellite markers flanking the three putative candidate genes viz., an Acetolactate Synthase (ALS) on chromosome 6 and two Acetohydroxy Acid Synthase (AHAS) genes, one on chromosomes 2 and another on chromosome 4. RM 6844 on chromosome 2 located 0.16 Mbp upstream of AHAS (LOC_Os02g30630) was found to co-segregate with herbicide tolerance. Cloning and sequencing of AHAS (LOC_Os02g30630) from the wild type, N22 and the mutant HTM and their comparison with reference Nipponbare sequence revealed several Single Nucleotide Polymorphisms (SNPs) in the mutant, of which eight resulted in non-synonymous mutations. Three of the eight amino acid substitutions were identical to Nipponbare and hence were not considered as causal changes. Of the five putative candidate SNPs, four were novel (at positions 30, 50, 81 and 152) while the remaining one, S627D was a previously reported mutant, known to result in Imidazolinone tolerance in rice. Of the novel ones, G152E was found to alter the hydrophobicty and abolish an N myristoylation site in the HTM compared to the WT, from reference based modeling and motif prediction studies.ConclusionsA novel mutant tolerant to the herbicide "Imazethapyr" was developed and characterized for genetic, sequence and protein level variations. This is a HTM in rice without any IPR (Intellectual Property Rights) infringements and hence can be used in rice breeding as a novel genetic stock by the public funded organizations in the country and elsewhere.

Project description:In this study, the differences in reactive oxygen species (ROS) generation and abscisic acid (ABA) accumulation in senescing leaves were investigated by early-senescence-leaf (esl) mutant and its wild type, to clarify the relationship among ABA levels, ROS generation, and NADPH oxidase (Nox) in senescing leaves of rice (Oryza sativa). The temporal expression levels of OsNox isoforms in senescing leaves and their expression patterns in response to ABA treatment were determined through quantitative real-time reverse transcription PCR (qRT-PCR). Results showed that the flag leaf of the esl mutant generated more O2- concentrations and accumulated higher ABA levels than the wild-type cultivar did in the grain-filling stage. Exogenous ABA treatment induced O2- generation; however, it was depressed by diphenyleneiodonium chloride (DPI) pretreatment in the detached leaf segments. This finding suggested the involvement of NADPH oxidase in ABA-induced O2- generation. The esl mutant exhibited significantly higher expression of OsNox2, OsNox5, OsNox6, and OsNox7 in the initial of grain-filling stage, followed by sharply decrease. The transcriptional levels of OsNox1, OsNox3, and OsFR07 in the flag leaf of the esl mutant were significantly lower than those in the wild-type cultivar. The expression levels of OsNox2, OsNox5, OsNox6, and OsNox7 were significantly enhanced by exogenous ABA treatments. The enhanced expression levels of OsNox2 and OsNox6 were dependent on the duration of ABA treatment. The inducible expression levels of OsNox5 and OsNox7 were dependent on ABA concentrations. By contrast, exogenous ABA treatment severely repressed the transcripts of OsNox1, OsNox3, and OsFR07 in the detached leaf segments. Therefore, OsNox2, OsNox5, OsNox6, and OsNox7 were probably involved in the ABA-induced O2- generation in the initial stage of leaf senescence. Subsequently, other oxidases activated in deteriorating cells were associated with ROS generation and accumulation in the senescing leaves of the esl mutant. Conversely, OsNox1, OsNox3, and OsFR07 were not associated with ABA-induced O2- generation during leaf senescence.

Dataset Information

Genetic and Physio-Biochemical Characterization of a Novel Premature Senescence Leaf Mutant in Rice (Oryza sativa L.).

Publications

Genetic and Physio-Biochemical Characterization of a Novel Premature Senescence Leaf Mutant in Rice (<i>Oryza sativa</i> L.).

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