Salinity-induced genes and molecular basis of salt-tolerant strategies in mangroves

Abstract

Salinity is one of the major environmental stresses that affects the growth and productivity of plant by affecting photosynthesis and other metabolic process. Halophytes are capable of thriving and growing under high concentration of NaCl. However, soil salinity is among the leading environmental stresses affecting global agriculture, causing billions of dollars loss per annum due to crop damages. Regardless of its high salinity in the root zone, it severely impedes normal plant growth and development due to ion, osmotic toxicity, and water deficit, resulting in reduced of crop productivity. Salt tolerance is a genetically complex trait in plants, often modulated by multiple biosynthetic and signaling pathways. Cross-talks among various stress-controlling pathways have been observed under salt stress, many of which are regulated by transcription factors. Thus, a comprehensive knowledge of the up- and downregulating genes under salt stress is necessary, which would provide a better understanding of the interactions among pathways in response to salt stress. DNA microarray technology has been employed to study expression profiles in different plant species and at varying developmental stages in response to salt stress. As a result, large-scale gene expression profiles under salt stress are now available for many plant species. Examinations of such gene expression profiles will help to understand the complex regulatory pathways affecting plant salt tolerance and potentially functional characterization of unknown genes, which may be good candidate genes for developing salt tolerance in plants. In this chapter, current knowledge of plant salt tolerance is discussed for a better understanding of the genetic basis of plant salt tolerance. The understanding of salt-tolerant mechanism particularly in producing antioxidative enzymes and special salt stress marker proteins is discussed in adapting adversely high-salinity environment in tree mangroves. A detailed antioxidative defense system against the production of active oxygen species (ROS) - an early indicator for adverse condition in both mangroves and mangroves associates - is discussed. This aspect has been studied using a true mangrove Bruguiera gymnorrhiza to detect the changes in antioxidative enzyme system as well as leaf and thylakoid protein profile as a case study. Approaches for improving plant salt tolerance using various salt stress genes as well as tools of biotechnology have been discussed.