Characters of the MOCA family in wheat and TaMOCA1 function in salt stress tolerance

MOCA1 encodes the last key glucuronosyltransferase for ionic stress sensor glycosyl inositol phosphoryl-ceramide (GIPCs) biosynthesis in Arabidopsis, which indicates that the MOCA gene family play important role in plant tolerance to salt stress. However, the isolation and function of MOCAs in staple crops have not been reported and the downstream targets of MOCAs in salt stress tolerance signalling pathway are not clear. In this study, we identified 110 MOCA genes in wheat which were classified into five clades and they differed in gene structure, protein length, conserved motifs and expression profiles in different tissues and under salt stress. TaMOCA1 was selected for further functional study in response to salt stress. TaMOCA1 was rapidly induced by NaCl treatment. The 35S::TaMOCA1-GFP construction showed the cell nucleus and cytoplasm location in wheat protoplast. TaMOCA1 over-expressing Arabidopsis seedlings formed longer primary roots and more lateral roots than the wild type ones under 50 mM NaCl treatment. The over-expressing Arabidopsis had higher expression levels of HKT1, but lower expression levels of NHX1 and SOS genes than the wild type. Also, the transgenic plants had higher SOD activity and lower MDA content than the wild Arabidopsis seedling under salt stress. These results may indicate that TaMOCA1 increases salt stress tolerance through decreasing Na⁺ loading from the xylem parenchyma cells to the xylem via SOS1 and HKT1, hence lowering root-to-shoot delivery of Na⁺ and superior antioxidant ability. All these results lay a foundation for further functional study of MOCAs in wheat.