Identification and characterization of the bZIP transcription factor family in yellowhorn

The basic leucine zipper (bZIP) transcription factor family is one of the largest and most diverse families in plants, regulating plant growth and development and playing an essential role in response to abiotic and biotic stresses. However, little is known about the biological functions of bZIP proteins in yellowhorn (Xanthoceras sorbifolium). Recently, 64 XsbZIP genes were identified in the yellowhorn genome and found to be disproportionately distributed in linkage groups. The XsbZIP proteins clustered into 11 groups based on their phylogenetic relationships with AtbZIP, ZmbZIP and GmbZIP proteins. Five intron patterns in the basic and hinge regions and additional conserved motifs were defined, both supporting the group classification and possibly contributing to their functional diversity. Compared to tandem duplication, the segment duplication greatly contributed to the expansion of yellowhorn bZIP genes. In addition, most XsbZIP genes harbor several stress responsive cis-elements in their promoter regions. Moreover, the RNA-seq and qRT-PCR data indicated XsbZIP genes were extensively involved in response to various stresses, including salt (NaCl), cold and abscisic acid, with possibly different molecular mechanisms. These results provide a new understanding of the biological functions of bZIP transcription factors in yellowhorn.

The Common Bean (Phaseolus vulgaris) Basic Leucine Zipper (bZIP) Transcription Factor Family: Response to Salinity Stress in Fertilized and Symbiotic N2-Fixing Plants

The basic leucine zipper (bZIP) transcription factor family regulates plant developmental processes and response to stresses. The common bean (Phaseolus vulgaris), an important crop legume, possesses a whole set of 78 bZIP (PvbZIP) genes, the majority of these (59%) are most highly expressed in roots and nodules, root-derived new organs formed in the rhizobia N2-fixing symbiosis. Crop production is highly affected by salinity in Cuba and other countries. In this work we characterized the adverse effect of salinity to common bean plants of the Cuban CC-25-9-N cultivar grown in fertilized (full N-content) or symbiotic N-fixation (rhizobia inoculated) conditions. We assessed if PvbZIP TF participate in CC-25-9-N common bean response to salinity. Quantitative reverse-transcriptase-PCR (qRT-PCR) expression analysis showed that 26 out of 46 root/nodule-enhanced PvbZIP, that responded to salt stress in roots and/or nodules from fertilized and N2-fixing CC-25-9-N plants. From public common bean transcriptomic data, we identified 554 genes with an expression pattern similar to that of salt-responsive PvbZIP genes, and propose that the co-expressed genes are likely to be involved in the stress response. Our data provide a foundation for evaluating the individual roles of salt-responsive genes and to explore the PvbZIP-mediated improvement of salt tolerance in common bean.