Mechanism Study Of AtHSPR Involved In Drought Response In Arabidopsis

Drought is an important abiotic stress.It has adverse effects on photosynthesis,respiratory metabolism and membrane structure etc.When plants are subjected to drought stress,they will take actions to reduce the hurt.Plants usually improve the content of ABA(abscisic acid)and then enhance ABA-dependent stomatal closure,which will reduce water loss.Also,plants will strengthen the ability of osmotic regulation to maintain osmotic balance and increase the ability of antioxidant system to lower oxidative damage.Drought stress has been a big threat worldwide,so seeking and studying novel genes will be a significant subject.Three different lines of Arabidopsis,WT(wild type),athspr mutant(Arabidopsis thaliana heat shock protein-related)and OE(overexpression),were used to drought treatment.We focused on their phenotype,physiology and biochemistry process and molecular basis so as to elucidate the function of AtHSPR in drought tolerance.Main results were showed as followed.1.Analysis for the cis-elements upstream of AtHSPR promoter gave some hints that there are many water-related motifs,so we speculated that AtHSPR may be related with drought tolerance in Arabidopsis.Histochemical staining of GUS showed that seedlings treated with drought(air dry)was darker than that of control and the relative expression level of AtHSPR increased more than 2times,which was consistent with preliminary assumption that AtHSPR promoter is really response to water deficiency(drought).2.Phenotype of drought tolerance was analyzed after PEG6000(25%w/v)and natural drought treatment.The result showed that overexpression of AtHSPR could enhance the drought tolerance of plant to some extent,while function deficiency of AtHSPR led to a decrease in drought tolerance.3.athspr mutant increased stomata density by 1.5 times and 1.8 times and stomata index by6.4%and 7.3%compared with WT and OE respectively.This means that athspr mutant had a higher water loss rate in the same condition.Overexpression of AtHSPR could efficiently enhance the ability of ABA-dependent stomata closure,while function deficiency would negatively affect this movement.4.Response to H₂O₂ was impaired in athspr mutant but was enhanced in OE.Overexpression of AtHSPR could promote the accumulation of proline to enhance osmotic adjustment and could promote the accumulation of anthocyanin and the activity of SOD and CAT to cut down the damage of H₂O₂.5.Relative expression levels of ABA biosynthesis gene(NCED3)and two stress-response genes(RD22 and RD29B)were quantified by q RT-PCR.The result showed that ABA biosynthesis was suppressed in athspr mutant,whereas overexpression of AtHSPR could facilitate ABA biosynthesis under drought condition.In addition,AtHSPR gene could positively regulate RD22and RD29B which are stress-response genes.Taken together,AtHSPR could reduce the stomatal density and index,so as to protect water from losing.AtHSPR could enhance the proline biosynthesis to maintain osmotic balance in plant cell.AtHSPR could promote the biosynthesis of anthocyanin and the activity of SOD and CAT to keep ROS homeostasis.AtHSPR could positively regulate some stress-response genes to make plants have a rapid perception and response.