Abstract

The fragrant Thai jasmine rice cultivar, Khao Dawk Mali 105 (KDML 105), is an economically important cultivar with valuable flavour characteristics, however, it is very sensitive to salinity. To investigate whether genetic characters for salt-tolerance are present, proteomes from the leaf lamina of KDML 105 and a contrasting salt tolerant cultivar (Pokkali) were compared under saline conditions. Ten differential proteins were identified, mainly representing gene products involved in photosynthesis, carbon assimilation and the oxidative stress response. The mRNA transcripts for these proteins were then monitored in both cultivars using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). For Pokkali, the up-regulation of nine identified salt-induced proteins was related to the increase in abundance of the respective mRNA transcripts. In contrast, although mRNA transcripts encoding all ten identified proteins could be detected in KDML 105, only three differential proteins spots were detected in the proteomic analysis. This indicates that although KDML 105 contains elevated transcript level of genes needed for salt tolerance, the posttranscriptional mechanisms controlling protein expression levels were not as efficient as in Pokkali, indicating targets for future genetic improvement.

Key words: Salt stress, fragrant rice, Oryza sativa L., Khao Dawk Mali 105 (KDML 105), proteomics, semi-quantitative RT-PCR.