Comparative transcriptional profiling under drought stress between upland and lowland rice (Oryza sativa L.) using cDNA-AFLP

Abstract

The continuous growth of lowland rice (LR) in paddy fields supplied with enough water over the years, and of upland rice (UR) in naturally rain-fed soils, has resulted in greater resistance to drought stress in UR compared to LR. To elucidate their differential regulation mechanisms of drought-resistance, genome-wide transcript regulation under drought stress in UR and LR was investigated using cDNA-AFLP. The results indicated that over 90% of gene expression was not affected by drought stress in the two rice genotypes, more than 8% was regulated by drought stress in both, and less than 1% was specifically expressed in UR or LR. Fifty-seven genes were specifically expressed in UR and thirty-eight specifically in LR. Genes specifically expressed in UR included cell rescue and defence genes functioning in drought-resistance, signal transduction molecules, nucleotides and amino acid biosynthesis genes required for plant growth, and the regulatory genes for growth and development. In LR, genes specifically expressed were related to protein and nucleotide degradation. Some genes were upregulated earlier in UR, and downregulated genes were inclined to be downregulated earlier in UR compared to LR, implying that more rapid regulation mechanisms caused earlier responses of UR to drought stress. Expression levels of upregulated genes in UR were higher than those in LR. The differences in gene expression between UR and LR could account for stronger regulation ability, more drought-resistance and superior growth of UR under drought stress compared to LR.