Drought Tolerance Enhancement with Co-Overexpression of DREB2A and APX in Indica Rice (Oryza sativaL.)

摘要

Rice is a major cereal crop providing food and energy to more than half of world’s population and drought is a challenging abiotic stress limiting rice production. Engineering drought tolerance trait is a major bottle neck because of multigenic control and complex nature. Two promising candidate genes utilized in engineering drought tolerance include DREB2A transcription factor (a master regulator of downstream stress inducible genes) and APX (an important ROS scavenging enzyme). Overexpression of DREB genes has shown encouraging results but with a negative impact on plant morphology and production. Moreover, co-expression of DREB2A and APX genes’ influence on drought stress has not been studied. Hence, in the present study, style="font-family:Verdana;"> overexpression of single genes DREB2A or APX and co-expression of these genes were studied for enhancement of drought tolerance in indica rice. Both genes under control of CaMV 35S promoter were transferred by style="font-family:Verdana;">Agrobacterium style="font-family:Verdana;"> transformation into rice variety BPT5204 popular for slender grains in South India. Confirmation of T-DNA integration into rice genome was done with PCR analysis of transgenes. Homozygous transgenic lines of DREB2A, > style="font-family:Verdana;">APX and DREB2A-APX generated in T _{style="font-family:Verdana;">3} style="font-family:Verdana;"> generation were evaluated for style="font-family:Verdana;"> drought tolerance during seed germination, vegetative and reproductive stages. In seed germination stage, transgenic lines exhibited higher germination rates on 200 style="font-family:;" "=""> style="font-family:Verdana;">mM mannitol MS medium in comparison to WT style="font-family:Verdana;">. style="font-family:Verdana;"> In vegetative stage, with-holding water for 7 days transgenic lines exhibited higher chlorophyll, proline, reducing sugars and enhanced activities of APX, SOD and catalase enzymes as well as reduced MDA content. The qRT-PCR analysis revealed higher relative transgene expression under drought stress. In reproductive stage, before maturity with-holding water for 7 days and restoring normal conditions style="font-family:Verdana;">, style="font-family:Verdana;"> transgenic lines developed longer panicles and style="font-family:Verdana;">a style="font-family:;" "=""> style="font-family:Verdana;">higher number style="font-family:Verdana;">of grains/plant compared to WT. The overall results indicate that style="font-family:Verdana;"> co-expression of DREB2A and APX can provide enhanced drought tolerance in rice plants to combat climate change conditions.