Rates of photosynthesis,tolerance to photooxidative stress,and senescence are all important physiological factors that affect plant development and thus agricultural productivity.GRAS proteins play essential roles in plant growth and development as well as in plant responses to biotic and abiotic stresses.So far few GRAS genes in wheat(Triticum aestivum L.)have been characterized.A previous transcriptome analysis indicated that the expression of a GRAS gene(TaSCL14) was induced by high-light stress in Xiaoyan 54(XY54),a common wheat cultivar with strong tolerance to high-light stress.In this study,TaSCL14 gene was isolated from XY54 and mapped on chromosome 4A.TaSCL14 was expressed in various wheat organs,with high levels in stems and roots.Our results confirmed that TaSCL14 expression was indeed responsive to high-light stress.Barley stripe mosaic virus(BSMV)-based virus-induced gene silencing(VIGS)of TaSCL14 in wheat was performed to help characterize its potential functions.Silencing of TaSCL14 resulted in inhibited plant growth,decreased photosynthetic capacity,and reduced tolerance to photooxidative stress.In addition,silencing of TaSCL14 in wheat promoted leaf senescence induced by darkness.These results suggest that TaSCL14 may act as a multifunctional regulator involved in plant growth,photosynthesis,tolerance to photooxidative stress,and senescence.
Kunmei ChenHongwei LiYaofeng ChenQi ZhengBin LiZhensheng Li
In order to explore the genetics of dark-induced senescence in winter wheat(Triticum aestivum L.),a quantitative trait loci(QTL)analysis was carried out in a doubled haploid population developed from a cross between the varieties Hanxuan 10(HX)and Lumai 14(LM).The senescence parameters chlorophyll content(Chl a+b,Chl a,and Chl b),original fluorescence(Fo),maximum fluorescence level(Fm),maximum photochemical efficiency(Fv/Fm),and ratio of variable fluorescence to original fluorescence(Fv/Fo)were evaluated in the second leaf of whole three-leaf seedlings subjected to 7 d of darkness.A total of 43 QTLs were identified that were associated with dark-induced senescence using composite interval mapping.These QTLs were mapped to 20 loci distributed on 11 chromosomes:1B,1D,2A,2B,3B,3D,5D,6A,6B,7A,and 7B.The phenotypic variation explained by each QTL ranged from 7.5% to 19.4%.Eleven loci coincided with two or more of the analyzed parameters.In addition,14 loci co-located or were linked with previously reported QTLs regulating flag leaf senescence,tolerance to high light stress,and grain protein content(Gpc),separately.
Hongwei LiFanyun LinGui WangRuilian JingQi ZhengBin LiZhensheng Li
In plants, the chloroplast is the main reactive oxygen species (ROS) producing site under high light stress. Catalase (CAT), which decomposes hydrogen peroxide (H2O2), is one of the controlling enzymes that maintains leaf redox homeostasis. The catalase mutants with reduced leaf catalase activity from different plant species exhibit an H2O2-induced leaf cell death phenotype. This phenotype was differently affected by light intensity or photoperiod, which may be caused by plant species, leaf redox status or growth conditions. In the rice CAT mutant nitric oxide excess 1 (noe1), higher H2O2 levels induced the generation of nitric oxide (NO) and higher S-nitrosothiol (SNO) levels, suggesting that NO acts as an important endogenous mediator in H2O2-induced leaf cell death. As a free radical, NO could also react with other intracellular and extracellular targets and form a series of related molecules, collectively called reactive nitrogen species (RNS). Recent studies have revealed that both RNS and ROS are important partners in plant leaf cell death. Here, we summarize the recent progress on H2O2-induced leaf cell death and the crosstalk of RNS and ROS signals in the plant hypersensitive response (HR), leaf senescence, and other forms of leaf cell death triggered by diverse environmental conditions.
Lesion mimic is necrotic lesions on plant leaf or stem in the absence of pathogenic infection,and its exact biological mechanism is varied.By a large-scale screening of our T-DNA mutant population,we identified a mutant rice lesion initiation 1(rlin1),which was controlled by a single nuclear recessive gene.Map-based cloning revealed that RLIN1 encoded a putative coproporphyrinogen Ⅲ oxidase in tetrapyrrole biosynthesis pathway.Sequencing results showed that a G to T substitution occurred in the second exon of RLIN1 and led to a missense mutation from Asp to Tyr.Ectopic expression of RLIN1 could rescue rlin1 lesion mimic phenotype.Histochemical analysis demonstrated that lesion formation in rlin1 was light-dependent accompanied by reactive oxygen species accumulated.These results suggest that tetrapyrrole participates in lesion formation in rice.
Growth light intensities largely determine photosynthesis, biomass, and grain yield of cereal crops. To explore the genetic basis of light responses of biomass and Researchphotosynthetic parameters in wheat(Triticum aestivum L.),a quantitative trait locus(QTL) analysis was carried out in a doubled haploid(DH) population grown in low light(LL),medium light(ML), and high light(HL), respectively. The results showed that the wheat seedlings grown in HL produced more biomass with lower total chlorophyll content(Chl), carotenoid content, and maximum photochemical efficiency of photosystem II(Fv/Fm) while the wheat seedlings grown in LL produced less biomass with higher Chl compared with those grown in ML. In total, 48 QTLs were identified to be associated with the investigated parameters in relation to growth light intensities. These QTLs were mapped to 15 chromosomes which individually explained6.3%–36.0% of the phenotypic variance, of which chromo-somes 3A, 1D, and 6B were specifically involved in LL response, 5D and 7A specifically involved in ML response,and 4B specifically involved in HL response. Several light-responsive QTLs were co-located with QTLs for photosynthetic parameters, biomass, and grain weight under various conditions which may provide new hints to uncover the genetic control of photosynthesis, biomass, and grain weight.
Hongwei LiGui WangQi ZhengBin LiRuilian JingZhensheng Li
