Senescence Mutant Screening And Gene Cloning By Chlorophyll Fluorescence Image Id Arabidopsis Thaliana

Leaf senescence in plant involves a coordinated action at the cellular, tissue, organ, and organismlevels under the control of a highly regulated genetic program. Major breakthroughs in the molecularunderstanding of leaf senescence were achieved through characterization of various senescence mutantsand senescence-associated genes, and identify regulatory factors such as transcriptional regulator,receptor, components that participate in hormone signal pathway, regulatory factors that participate instress and metabolism regulation in the gene level. It reveals the essence of regulatory factors in theprocess of leaf senescence and the highly complex signal control network. Although there are alreadymany researches on senescence, there are still many problems such as the mechanism of senescencerelated cell death, the collaborative regulation mechanism of cells, tissues, organs and organism and theeffect of the light on senescence.The most obvious sign of senescence is that the leaves’ color turns to yellow from green.Chlorophyll degradation and photosynthetic ability decreases accordingly. The chlorophyll fluorescenceis used to monitor the changes of photosynthesis ability and screen senescence associated mutants. Theexperimental material in this study was Arabidopsis mutants library that was gotten by treatingArabidopsis seeds with chemical mutagenesis agent sulfonic acid ethyl ester (EMS). We usedchlorophyll fluorescence imaging to screen and separate senescence associated mutants. By observingthe chlorophyll fluorescence parameters Fv/Fm (maximum quantum efficiency of PSII photochemistry)in the whole growth period of the Arabidopsis Col-0, we found that the value of Fv/Fm saturated on the28th day, then the parameters Fv/Fm began to drop. Thus we regarded this time as the beginning of the senescence. Further experiment about analysis on the fluorescence parameters in darkness for threedays, we found that the process in dark for three days is the best screening condition for experiment.Therefore, we screen senescence associated mutants by measuring Fv/Fm of the plant of the28days oldin dark for three days. By numerous screening work we have got14lines potential mutants currently,we studyed mainly on the mutants sef1(senescence fluorescence mutant1, sef1) and sef2, analysed itsphysiological functions and cloned it. In contrast with WT, the chlorophyll fluorescence parametersFv/Fm of sef1is obviously lower, the chlorophyll and soluble protein degradation speeded up, ionleakage enhanced. RT-PCR showed that the expression of senescence associate gene (SAG) rised in themutants than WT, the mutant gene was now preliminary located in the chromosome2. The Fv/Fm ofsef2was significantly higher than WT, chlorophyll and soluble protein content in sef2was higher thanWT, the ion leakage was lower than WT, and the SAG expression in the mutant was down regulation,now it was preliminary located on chromosome2.To sum up, SEF1and SEF2were involved in the regulation of leaf senescence, and thephysiological and functional analysis about them could help us to better understand the mechanism ofplant senescence.