A C2-domain phospholipid-binding protein MdCAIP1 positively regulates salt and osmotic stress tolerance in apple

Abstract

High salt restricts the growth and development of plants. A diverse range of genes are involved in the response to salt stress. Here we report that MdCAIP1 (C2-domain ABA Insensitive Protein1), a single C2-domain containing protein, has a conserved structure consisting of an eight-stranded anti-parallel β-sandwich. MdCAIP1 was able to bind to phospholipids in a Ca2+-dependent manner and localized to the plasma membrane. qRT-PCR analysis showed that MdCAIP1 was induced by abiotic stresses including salt, osmotic, and drought stress, as well as the hormone JA. Transgenic apple calli and Arabidopsis over-expressing MdCAIP1 were more tolerant to salt and osmotic stress, and had higher proline content and lower MDA content under these stressful conditions. Furthermore, MdCAIP1 could homodimerize. These results indicate that MdCAIP1 is a Ca2+-dependent phospholipid-binding protein, and implicate it in tolerance to salt and osmotic stress. MdCAIP1, a Ca2+-dependent phospholipid-binding protein, could homodimerize and positively regulated salt and osmotic tolerance in plants.