Gene transcription in the leaves of rice undergoing salt-induced morphological changes (Oryza sativa L.)

We describe the gene expression profile of third leaves of rice (cv. Nipponbare) seedlings subjected to salt stress (130 mM NaCl). Transcripts of Mn-SOD, Cu/Zn-SOD,cytosolic and stromal APX, GR and CatB were regulated, whereas expression of thylakoid-bound APX and CatA were down-regulated. The levels of the compatible solute proline and of transcripts of its biosynthetic gene, Delta1-pyrroline-5-carboxylate synthetase (P5CS), were strongly increased by salt stress. Interestingly, a potential compatible solute, gamma-aminobutyric acid (GABA), was also found to be strongly induced by salt stress along with marked up-regulation of transcripts of GABA-transaminase. A dye-swap rice DNA microarray analysis identified a large number of genes whose expression in third leaves was altered by salt stress. Among 149 genes whose expression was altered at all the times assayed (3, 4 and 6 days) during salt stress, there were 47 annotated novel genes and 76 unknown genes. These results provide new insight into the effect of salt stress on the expression of genes related to antioxidant enzymes, proline and GABA as well as of genes in several functional categories.