Identification and characterization of the LDAP family revealed GhLDAP2_Dt enhances drought tolerance in cotton.

Lipid droplet-associated proteins (LDAPs) play essential roles in tissue growth and development and in drought stress responses in plants. Cotton is an important fiber and cash crop; however, the LDAP family has not been characterized in cotton. In this study, a total of 14, six, seven, and seven genes were confirmed as LDAP family members in , , , and , respectively. Additionally, expansion in the LDAP family occurred with the formation of , which is mirrored in the number of LDAPs found in five Malvaceae species (, , , , and ), , and . The phylogenetic tree showed that the genes in cotton can be divided into three groups (I, II, and III). The analysis of gene structure and conserved domains showed that derived from group I (//) are highly conserved during evolution, while members from groups II and III had large variations in both domains and gene structures. The gene expression pattern analysis of genes showed that they are expressed not only in the reproductive organs (ovule) but also in vegetative organs (root, stem, and leaves). The expression level of two genes in group III, , were significantly higher in fiber development than in other tissues, indicating that it may be an important regulator of cotton fiber development. In group III, /, especially was strongly induced by various abiotic stresses. Decreasing the expression of in cotton virus-induced gene silencing increased the drought sensitivity, and the over-expression of led to increased tolerance to mannitol-simulated osmotic stress at the germination stage. Thus, we conclude that plays a positive role in drought tolerance.