Rice Genetics IV - IRRI books - International Rice Research Institute

Log(2) ratio1.51.0OC104E01—WCP1OC03G03—WCP2OC104A02—WCP3OC03F03—WCP40.50–0.5–1.0–1.510.5WCP1WCP2WCP3WCP415136241 w11.5 12.5 13.5 14.5 15Log(2) signal intensityFig. 2. Regulation and intensity of selected (putative) water channel proteinsduring a salt stress time course from rice cultivar Pokkali. Compared are fourputative water channel protein transcripts. WCP1 shows high similarity toplasma membrane-located WCP and WCP2–4 are similar to tonoplast-specificWCP. Intensity and ratio of regulation relative to no-stress controls are shownfor six time points during salt treatment. WCP1, 2, and 4 are surrounded as agroup (and arrow for the 7-d time point for WCP4); time points for WCP3 areindividually enclosed by circles.all hybridization intensity and background levels of different slides, normalizationcan be achieved, assuming an overall similar or identical intensity even though individualtranscripts may be variable. We compare the log(2) ratio (up- or downregulation)and the log(2) absolute signal intensity for four different putative water channel proteins.Plotted are the intensities and ratios for six time points during the stress experimentof rice cultivar Pokkali. For all putative water channel protein transcripts, intensitydeclined initially during salt stress. Lower expression levels for water channelproteins following salinity stress have been observed in other models (e.g., Yamada etal 1995). After only 1 wk (and after 24 h for WCP3 and WCP4), all water channels aremore highly expressed than before stress and increases in abundance are obvious.Most significant, however, is the intensity distribution: the four water channel proteintranscripts occupy intensity ranges that are similar in all comparisons, which werederived from six different microarray hybridizations. Also, WCP1 is a less abundanttranscript than the others, and it encodes a plasma membrane-specific WCP. WCP2–4 encode tonoplast-specific transcripts that are typically more highly expressed thanthose located in the plasma membrane. From these experiments, it seems justified tostate that comparisons are possible and that they generate data that can be incorporatedinto hypotheses on salt stress responses.Isolation of candidate genes for tolerance of abiotic stresses 357