Rice Genetics IV - IRRI books - International Rice Research Institute

Transgenic approachesfor generating rice tolerantof dehydration stressZ.Q. Cheng, J. Targolli, J. Su, C.K. He, F. Li, and R. WuTransgenic approaches offer new opportunities to improve tolerance for dehydrationstress in rice by incorporating genes that are involved in stresstolerance. In this chapter, we present the results of transforming rice separatelywith plasmids containing genes that encode a group 3 LEA (late embryogenesisabundant) protein, a group 2 LEA protein, a group 1 LEA protein,and a delta 1-pyrroline-5-carboxylate synthetase (P5CS). In each experiment,the growth of transgenic plants under dehydration stress was shown to befaster than that of nontransformed control plants. To maximize gene expressionand plant growth, we compared the results of using a constitutive promoterand a stress-inducible promoter in driving the expression of the P5CSgene. Next, the effect of using a matrix attachment region sequence ontransgene expression was tested. Finally, we compared two commonly usedmethods for transforming rice.Plant productivity is strongly influenced by dehydration stress induced by droughtand high-salt and low-temperature conditions. Plants respond to these stresses bydisplaying complex quantitative traits that involve many genes. These responses resultin a wide variety of biochemical and physiological changes, such as the accumulationof various low-molecular-weight organic compounds, collectively known asosmolytes, synthesis of different late embryogenesis abundant (LEA) proteins, andactivation of several detoxification enzymes (Bajaj et al 1999, Reddy et al 1999).Abiotic stresses reduce the productivity of several major crops (Boyer 1982, Yanceyet al 1982). Thus, understanding and improving stress tolerance in crop plants presentsa challenging basic research problem that could also have a significant impacton agricultural productivity.Ingram and Bartels (1996) and Bray (1997) have reviewed the molecular andphysiological basis of dehydration stress tolerance. Gene expression and signal trans-Transgenic approaches for generating rice . . . 423