Evolutionary analysis of MOCA1 gene in Arabidopsis thaliana and functional comparison with PGSIP7 and PGSIP8 genes.

Soil salinization is becoming a more serious environmental issue. Excessive salt will hinder the growth and development of plants, reduce crop yields, limit global agricultural production, and increasingly threaten the sustainability of global food supplies. Salt sensing refers to the process in which external Na+ stimulates plants. GIPC binds Na+ to activate Ca2+ channels, leading to Ca2+ influx; this cytosolic Ca²+ signal is subsequently transmitted to the SOS signaling pathway, triggering intracellular Na+ efflux and vacuolar storage. The salt tolerance of plants is a trait that emerged gradually through evolutionary adaptation, rather than an inherent property of the first land plants. Although terrestrial plants appeared about 450-470 million years ago, the origin and evolution of plant salt sensing remain unclear. In this study, two potential salt-sensitive genes, PGSIP7 and PGSIP8, in glycosyltransferase family 8 were identified through bioinformatics analysis. Further salt stress treatment found that the PGSIP7 gene responded to salt stress, which showed limited growth and development and decreased Na+ transport capacity in the SOS pathway, while the PGSIP8 gene was insensitive to salt stress. In addition, the origin and evolution of the MOCA1 gene were preliminarily explored by cloning homologous genes of the Arabidopsis salt-sensing gene MOCA1 from lower to higher plants to obtain transgenic plants. It was found that the MOCA1 gene originated from the single-celled plant Chlamydomonas reinhardtii, and its homologous gene is Cre10g422450v5. The MOCA1 gene has weak salt-sensing ability in lower plants, but with evolution, its ability to sense Na+ gradually increases in higher plants. Although the MOCA1 gene has different salt sensitivity in different plants, its overexpression can improve salt tolerance. Our results have laid a certain experimental framework for subsequent investigations concerning the evolution of salt-sensing genes in plants and the identification of new salt-sensitive genes. They also provide research ideas for enhancing crops' resistance against salt.