Gene expression analysis reveals diversified responsiveness to salt stress in rice genotypes

Abstract

Salt stress is a major factor affecting rice (Oryza sativa) growth and productivity, limiting its distribution globally. Rice production is primarily gets affected due to its vulnerability to salinity stress at seedling stage, as well as reproductive stage leading to reduction in yield. We report the analysis of 12 diverse rice genotypes collected from different parts of coastal places of northern Andra Pradesh and southern Orissa in India for salt tolerance and categorized their tolerance levels on the basis of reduction in growth and transcript expression pattern. The analysis identified four contrasting salt tolerant genotypes and other eight genotypes exhibited moderate tolerance. Two tolerant and two sensitive genotypes were biochemically explored and used further for gene expression analysis. Proline content showed significant difference between salt tolerant and sensitive genotypes suggesting high tolerance level in tolerant CR1014 and Kudrat-5. The gene-expression analysis of selected CR1014 (salt-tolerant) and Kudrat-5 (salt-sensitive) genotypes differed at transcript expression levels for antioxidant specific A2YPX2/plant peroxidase—POX (19.03-fold) and SODCP/superoxide dismutase (SOD) copper/zinc binding (3.77-fold) in shoots of Kudrat-5 and CATA1/catalase (2.49-fold) and SODCP/SOD copper/zinc binding (4.83-fold) in CR1014 in stress conditions). The salt-stress responsive-specific transcripts HAK17/K+ potassium transporter, A2XMP7/heat shock protein DnaJ, cysteine-rich domain and Q10D68/serine hydroxymethyltransferase in CR1014 after treatment showed increased expression. Interestingly, the transcripts specific for methionine biosynthesis mainly A2Z9C9/Cys/Met metabolism, pyridoxal phosphate-dependent enzyme and B8AF89/spermine synthase induced their expression in Kudrat-5 under salinity stress, where the similar trend was not reflected in salt-tolerant genotype. Thus, the present study highlights on transcript expression pattern for salt-stress responsive candidate genes in two-contrasting rice genotypes selected from the pool of farmer’s cultivated varieties along the coastal belts of India.