Microarray and suppression subtractive hybridization analyses of gene expression in Puccinellia tenuiflora after exposure to NaHCO 3

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To investigate genes expression in Puccinellia tenuiflora exposed to saline-alkali, NaHCO 3-induced stress, four suppression subtractive hybridization (SSH) libraries were constructed. Non-treated P. tenuiflora cDNA was used as the driver, and cDNAs from P. tenuiflora exposed to 0.4 mol/l NaHCO 3 for 6, 12, 24 and 48 h were used as the respective testers. Randomly selected clones from each SSH library were sequenced, and 1850 expressed sequence tags (ESTs) were obtained and analyzed. Approximately 400 ESTs from each library were randomly selected for placement on the cDNA microarray. In total, 158 differentially expressed genes were identified, and 93, 56, 21 and 71 genes were differentially expressed with NaHCO 3 stress for 6, 12, 24 and 48 h, respectively. These differentially expressed genes were categorized as putative novel (31.6%), photosynthesis (15.8%), unknown (15.2%), metabolism (12.7%) and defense genes (8.9%). The other differentially expressed genes were involved in a variety of functional areas, such as transport, transcriptional regulation, and protein synthesis. These results demonstrate that the response to NaHCO 3 stress in P. tenuiflora is a complex network involving multiple physiological and metabolic pathways. The differentially expressed genes were grouped using hierarchical cluster analysis, and six different clusters were defined. Approximately 80% of grouped genes belonged to two independent expression patterns, indicating that these two expression patterns may represent two important stress tolerance pathways or networks in P. tenuiflora.