Further insights into the association of the protein phosphatase gene ABI1 with drought and salinity stress responses in Brassica species

Systems biology can uncover major regulatory components involved in plants stress responses, resulting in novel insights into how plants tolerate stresses. This study aimed at analyzing the transcriptomes of Brassica rapa, the donor of A genome of rapeseed (Brassica napus), to illustrate the molecular basis of drought and salinity stress responses and to identify a hub regulatory gene for characterization in B. napus. Accordingly, the B. rapa microarray data of separate drought and salinity experiments were meta-analyzed. Consequently, 562 differentially expressed genes were identified and functionally annotated by gene ontology enrichment analysis and identification of regulatory genes. Abscisic acid, ethylene, and Ca2+ were known as the major signal molecules regulating adaptive responses to drought and salinity. Gene network analysis revealed that the protein phosphatase gene, ABA insensitive 1 (ABI1) is a hub regulatory gene involved in stress-related processes. The coding sequence of one copy of B. napus ABI1 (BnABI1) with 1281 bp long, located on A1 chromosome, was cloned and sequenced. BnABI1 gene exhibited different expression profiles between leaves and roots and also between two B. napus cultivars in response to drought and salinity stresses during the time-course experiments. Correspondence analysis and regression trees showed significant associations among the BnABI1 expression patterns and physiological indicators of tolerance to drought and salinity stresses in B. napus. Taken together, the results provided evidence that BnABI1 may contribute to the regulation of response and tolerance to drought and salinity stresses.