Regulatory Mechanisms Of Light Signal On The Chloroplast Of Selaginella Tamariscina In The Rehydration Process

DT plants(Desiccation-tolerant plant/resurrection plants)can survive in extreme dry conditions.During the dry period,the plant cell loss more than 90%water and become dormant.When the water conditions are suitable,the physiological functions of the cells,organs and whole plants are regained.As the most important organelle of plant,the choice of coroplasts decides lives of plant,in dehydration and rehydration process.Existence strategy of DT plants were divided into HDT plants(homoiochlorophyllous desiccation-tolerant plants)and PDT plants(poikilochlorophyllous desiccation-tolerant plants).Furthermore,Selaginella tamariscina(Lycopodiatae,Selaginella)is one of the oldest species vascular DT plant.Therefore,study on regulatory mechanisms of environmental light on the chloroplast structure,function and related gene expression of S.tamariscina in the rehydration process is significantly,which can support us in deeper studying the evolution of DT of terrestrial plants and the morphogenesis mechanism of chloroplast.This study takes S.tamariscina as the research object and analyzes the regulatory of light on the structure and function of chloroplasts and related gene expression in S.tamariscina during rehydration process and revels this mechanism in transcript level.The content of this research mainly has the following four parts:(1)This study analyzed the ultrastructure of chloroplasts in dehydrated and rehydrated S.tamariscina.The results show that the chloroplast ultrastructure remain intact in dehydrated samples.It reveals that S.tamariscina is an HDT plant.In the rehydration samples,chloroplasts ultrastructure has no obvious difference between S.tamariscina rehydrated in dark and light conditions.In short,light has no obvious effect on the recovery of chloroplast structure.(2)Analysis chlorophyll content and parameters measured by photosynthetic gas exchange and chlorophyll fluorescence measurement system;results show that the chlorophyll content slightly decreased.In the rehydration samples,the light led to a higher chlorophyll content than dark condition rehydrated samples.That indicated light promotes the biosynthesis of chlorophyll.The study found that the dehydrated samples lose photosynthetic capacity and activity of PSII;the activity of photosynthesis and PSII can be fully restored in light condition,but partly restored without light.It shows that light plays a certain role for recovery of photosynthetic structure and capacity.(3)588 differential genes of rehydration samples were revealed by transcriptome technology.when rehydrated in light samples compared with in dark,295 significant up-regulated genes and 293 significantly down-regulated genes were annotated.In addition,results suggest that light affects functions such as cell metabolism,stimulatory response by GO database,as well as the number of genes related to energy metabolism and carbohydrate metabolism in KEGG database,Lights mainly affect gene expression of the carotenoid biosynthesis,photosynthesis,flavonoids and flavonol biosynthesis,photosynthesis-antenna protein and circadian rhythm pathways.The expression and localization of all genes in the photosynthetic antenna protein and photosynthesis pathways of S.tamariscina grown in a culturing Room,dehydrated S.tamariscina and S.tamariscina rehydrated in light and dark conditions were analyzed.This study suggests that the difference in the expression of nuclear genes by lights is more significant than that of chloroplast genes.This study suggests that at the transcription level,light plays an important role in the resuscitation process mainly by acting on the cis-signal pathway.In summary,this study used the S.tamariscina grown in a culturing room,dehydrated S.tamariscina and S.tamariscina rehydrated in light and dark conditions as experimental material to measure and observe the chlorophyll content,chloroplast ultrastructure,photosynthesis,chlorophyll a fluorescence parameters and gene expression by transcriptome and real-time quantitative fluorescent PCR technology,revealing that environmental lights play an important role in the recovery process.The important role is achieved at the transcription level by the cis signal pathway in which the light affects the nuclear gene.