Calcium sensors in barley: genome-wide identification and expression analysis of the CBL gene family

In plants, Calcineurin B-like (CBL) proteins are crucial calcium sensors that assist in growth and stress response. The research systematically characterized ten CBL genes in barley (Hordeum vulgare) that were named HvCBL1-1 to HvCBL10. Phylogenetic classification put these genes into four subfamilies. Members of the same subfamily have similar facets on the molecular level. Whereas promoter regions of all the genes are enriched with diverse sets of cis-elements that were identified to be involved in hormone signaling or abiotic stress. Tissue-specific patterns were identified by expression profiling and predicted response to stress. Significantly, qPCR revealed that HvCBL1-2,HvCBL4-1, and HvCBL7 are strongly induced by salt stress in specific tissues, suggesting their involvement in salinity response. Transgenic barley lines were created to better understand the role of HvCBL4-1. Under the 200 mM NaCl stress, transgenic seedlings had significantly more salt tolerance than wild-type plants, as shown by substantial increases in fresh weight and root lengths. Transgenic plants exhibited a faster rate of proline accumulation compared to control plants. At molecular level, the expression of important genes involved in proline biosynthesis (HvP5CS) and ion homeostasis (HvSOS1) was notably and significantly enhanced. These findings not only add to the list of plant CBL proteins but also show that HvCBL4-1 positively regulates barley salt tolerance, possibly through the regulation of osmotic balance by proline synthesis and activation of SOS signaling. This work offers a foundation for understanding CBL/CIPK regulatory network in barley stress responses.