Expression Profiling Of Rice BHLH Transcription Factor Gene Family Under Stresses

Transtription factors have a central regulating role in plant development, differentiation and response to environmental stresses. The bHLH gene family is one of the biggest transcription factor families in plant.The rice variety, Nipponbare (Oryza sativa ssp. japonica), was used as material in this study. A macroarray chip containing 140 bHLH genes was printed using the PCR products recovered from specific PCR reaction. And five-leaf seedling was treated by 20% PEG simulated drought stress, total RNA was extracted from the treated and control leaves collected at different time points after treatment and used as target for the bHLH macroarray hybridization. Results showed that 16 bHLH transcription factor genes were differentially expressed under PEG-simulated drought treatment and the expression change of the bHLH gene was detected at least at one time point of the treatment by two-fold alteration. To validate the macroarray result, reverse transcriptional PCR was used to confirm the expression pattern change of the differentially expressed genes. The results showed that the 16 transcription factor genes were differentially regulated under PEG treatment and might be related to drought stress tolerance in rice.To comparatively analyze the expression patterns of candidate bHLH genes, which were differentially expressed under drought stress, under PEG-simulated drought stress and ABA treatment, quantitative real time PCR was used to profile their expression changes of the rice seedling under the treatment. Results showed that the alteration of genes expression under PEG stress was consistent with that of drought stress detected by macroarray analysis; But in most cases the candidate bHLH genes were down-regulated under ABA treatment, which was obviously different from that under drought or PEG stress, it was speculated that these bHLH genes might be involved in the responsiveness to PEG and ABA stress by the same or different molecular pathway or mode.We found three bHLH genes were commonly differentially expressed under real drought stress and PEG-simulated drought stress using whole genome oligo chip and bHLH macroarray chip respectively, these three bHLH genes will be more valuable for further gene function analysis. Our results will provide a basis of these bHLH gene cloning and dissection of their molecular mechanism in plant growth and development.