ABSTRACT
ARCHANA SINGH, VEDA KRISHNAN, VINUTHA THIMMEGOWDA, and SURESH KUMAR
ABSTRACT
Salt tolerance is a multigenic complex trait; hence only limited success has been achieved so far in developing salt-tolerant crop varieties through conventional breeding methods. Ion homeostasis is considered to be crucial for normal growth and development of plants under salt stress. Osmoprotectants, enzymatic, and non-enzymatic antioxidants, and other antistress molecules constitute the defense system of plants. Identification of the genes associated with the stress tolerance has provided new insights into the biological mechanism to cope up with the stress. Genomic studies promise to complement the use of existing genetic diversity to accelerate plant improvement programs toward the development of salt tolerant, high yielding, multistress tolerant plants. Development of transgenic plant with ion transporters, compatible organic solutes, and enhanced antioxidant production appears to be a promising approach to engineer biosynthetic pathways. Combined together, these may integrate ion homeostasis, reactive oxygen species scavenging, reduced lipid peroxidation, and maintaining protein structure and functions to efficiently counteract the stress. Evidence also suggests that genomic DNA not only provides the genetic information for a trait but also serves as chromatin modulator to affect the expression of the associated genes. Epigenetic (DNA methylation, posttranslational histone modifications, and regulatory/noncoding RNAs biogenesis) changes are induced by environmental perturbations. Hence, the ultimate success
of manipulating genes for stress tolerance in plant will only emerge if the transferred genes contribute to the stress tolerance not only at a particular stage of plant growth but also on the appearance of the stressful condition. Since the epigenetic state of chromatin is dynamic, transfer of a gene from one species to another would not only require the transfer of the gene(s) associated with a trait of interest but also the epigenetic state so that the genes can express optimally. In this chapter, we present newer insights for the successful development of salt-tolerant plants while utilizing the benefits of genetic engineering approach. The scope, challenges, and future prospects of genetic engineering, as a supplementary strategy to conventional breeding, have also been described.
