Analysis Of CBL10 Gene Duplication In The Halophyte Eutrema salsugineum

Abstract

The buildup of salt in soils is a major abiotic stress that affects agricultural productivity, limiting the growth and yield of most crop species which cannot tolerate even modest levels of salinity (glycophytes). Genetic variability for salt tolerance exists as some plants (halophytes) have adapted to environments with high levels of salt. Understanding how salt tolerance has been acquired in halophytic species will be an important part of strategies to improve the ability of crops to grow in saline soils. The CALCINEURIN B-LIKE10 (AtCBL10) calcium sensor was identified as a component of salt signaling in the glycophyte Arabidopsis thaliana (A. thaliana) based on hypersensitivity of the Atcbl10 mutant to salt. When A. thaliana is grown in the presence of salt, AtCBL10 interacts with the AtSOS2 protein kinase to activate the AtSOS1 sodium/proton exchanger, resulting in the removal of sodium ions from the cytosol. Eutrema salsugineum (E. salsugineum), a halophytic relative of A. thaliana, has two CBL10 genes (EsCBL10a and EsCBL10b). In this research, the duplication of CBL10 in E. salsugineum was characterized and the functions of EsCBL10a and EsCBL10b in salt tolerance were determined. My analyses indicate that the coding sequences of EsCBL10a and EsCBL10b are highly conserved, as they share 85% nucleotide identity. An analysis of transcript structure indicates transcripts from EsCBL10a and EsCBL10b loci are alternatively spliced, but in distinct ways. My results suggest that EsCBL10a and AtCBL10 likely share the ancestral genomic position, while EsCBL10b might have moved to a different genomic region, and that the duplication took place prior to the divergence of expanded Lineage II species. The expression patterns of EsCBL10a and EsCBL10b are different; EsCBL10b transcript is high in shoots and low in roots while EsCBL10a transcript is detectable in both tissues. Preliminary analysis of E. salsugineum lines with reduced expression of EsCBL10a and EsCBL10b suggest that both genes might play a role during growth in the presence of salt, but that these roles are distinct.