Towards understanding the transcriptional control of abiotic stress tolerance mechanisms in food legumes

Abstract

A multitude of environmental and subsoil conditions cause abiotic constraints to the growth and productivity of legume food species. These stresses often occur simultaneously, leading to compounded effects of low and unreliable yields. Since legumes are a major food source, particularly in regions of major population growth, it is imperative that better tolerant and adapted varieties are developed. For this, transgenic approaches integrated within traditional breeding programs are proposed to offer substantial productivity gains through fast-tracking the development and deployment of well adapted and tolerant varieties to regions of greatest need. For this to occur, knowledge of the major tolerance genes and more importantly their regulators is required. Accordingly, recent functional genomics approaches have begun to shed light on the transcriptional, and hence regulatory and mechanistic controls governing tolerances to several of the major abiotic stresses, such as drought, temperature and salinity within temperate legume food species. Functional validation of these regulatory signals, their action on downstream genes and associated pathways is underway within several large international programs. This chapter will review these advances in knowledge to date within the model and crop grain legume species, to identify and characterize the molecular targets for the future selection and breeding of sustainably tolerant crops. Specifi cally, this chapter aims to summarize progress towards identifying and understanding the functions of the WRKY transcription factors involved in instigating and regulating abiotic stress tolerance mechanisms and their potential for improving abiotic stress tolerance within temperate legume food species.