Global genome expression analysis of rice in response to drought and salinity
regretfully performed under an irrelevant stress protocol
A large group of scientists from several distinguished academic institutions in People’s Republic of China reported an extensive investigation on “Global genome expression analysis of rice in response to drought and high-salinity stresses in shoot, flag leaf, and panicle” (Plant Mol. Biol. (2007) 63:591–608). Hundreds of genes were found to be induced or repressed in the shoot, the flag leaf and the panicle of rice subjected to drought and salinity treatment protocols in the laboratory. However, despite the comprehensive genomic analysis of the data, the study is totally irrelevant to any real-life implication due to the unrealistic and unacceptable stress protocol used in this study. Plants were subjected to drought stress by taking them out of the growth medium and laying them with their roots on filter paper. Plant were analyzed when maximum stress was reached in about 4 h. A drought stress of 4 h hardly occurs in rice production or in any crop production for that matter. To induce salinity stress plants were taken out of their hydroponics culture and placed in saline culture for up to 24 h before they were analyzed. It has already been shown by Munns (2002) that the identification of whole plant salinity tolerance requires a long duration exposure to salinity (e.g. about three weeks in wheat). Long and slow exposure to drought and salinity as a perquisite for any tolerance assessment has been repeatedly underscored in many articles, reviews and conference meetings in the last decade. It is therefore remarkable that a 4 h or 24 h stress exposure is still being used in genomic plant stress research.