Studies On Functions Of LEA Gene In Ploygonum Sibircum In Plant Photoprotection Under Drought

Under drought stress, excess light enery obsorbed by havesting pigments have been occurred to use for carbon assimilation to form reactive oxygen species(ROS).The result is that photo-apparatus in plants were spoilted to forming a photo-oxidation even light Destruction photosynthetic apparatus forming a photo-oxidation even light damage. In the long-term natural evolution plants have built a series of defense mechanisms when light damage ocurred. However this self-regulating will be limited in some extent.A class of hydrophilic proteins accumulating late in embryogenesis of cotton seed were initially discovered in seeds of upland cotton to call late embryogenis abundant proteins(LEA).Under drought stress LEA like substances of osmotic adjustment in plant cells can increase or avoid moisture loss to protect plant cells form dehydration damage to maintain metabolic function.But studies of LEA proteins in plants on protection plant photosynthesis during drought stress, especially photoprotection are rarely reported.In this paper,The LEA protein gene cloned from Polygonum Siberia leaves (ps-LEA) was transformed to tobacco,and to formed genetic plants.The plants screened by kanamycin test,and PCR were obtained to drought treatment using wild tobacco plants as control(CK).Photosynthetic electron flow distribution, the excess energy dissipation and photosynthetic energy distribution will be inrestigated to reveal the ps-LEA function in plant photoprotection in leaves of transgenetic tobacco,the results as fllows:The results showed that above- and below ground growth in wild tobcoo plants were inhibited under soil drought and PEG simulated drought treatments to reduce plants biomass and net photosynthetic rate (Pn)in leaves of wild tobacoo was reduced significantly by both drought.lt was found that Pn decreasing were cacused by maxium photochemical efficiency (Fv/Fm) and electron transport rate(ETR) in leaves of wild tobacco plants occurred to photoinhibition.But in research ps-LEA reduces smaller than CK, maxium photochemical efficiency (Fv/Fm) and electron transport rate(ETR) in leaves of ps-LEA tobacco plants decreased smaller than that of CK,and Fv/Fm changed little under mild drought.It is indicated that ps-LEA played important roles in photoprotection of tobacco during drought stress.Further testing photochemical indicators found,Because of the ps-EEAis hydrophilic proteins (soluble protein increased). Prevents cell dehydration protect the damage of photosynthetic apparatus. Mainly in ps-LEA gene reduces PS Ⅱ reaction center and light absorption and electron transfer associated protein complex degradation, increased the openness remaining active reaction centers, maintaining relative stability of the electron transfer process, While the ps-LEA also increased the leaf capture light proportion absorb light energy for electron transfer to improve the heat dissipation capability mitigate the damage caused by drought stress effectively improving the drought tolerance of tobacco plants.