Genome-Wide Identification and Expression of the Mulberry PLA Family Under Drought and Salinity

Mulberry (Morus spp.) is valued for sericulture, medicine, and ecological restoration of degraded lands. Phospholipase A (PLA) enzymes hydrolyze membrane lipids and play critical roles in plant growth and stress responses, yet the PLA family in mulberry remains uncharacterized. Here, we performed genome-wide identification of Morus notabilis PLA genes in order to systematically analyze their phylogenetic relationships and gene structures, and profile their expression across tissues and under drought and salt stress, thereby providing candidate genes for future functional studies on stress tolerance. Fifty non-redundant PLA genes were identified and classified into three subfamilies: pPLA (22), PLA2 (nine), and PLA1 (19). Most predicted PLA proteins are small (100-500 aa) with predicted instability. Gene structures varied from 1 to 21 exons, and subfamily specific conserved domains (patatin/C2, PLATZ, lipase_3) were detected. Promoters contained stress- and hormone-responsive elements. Expression patterns across five tissues revealed distinct preferential patterns: 56% of genes showed highest expression in roots, with one-fifth in leaves. Under stress, 10 and 12 MnPLA genes were increased >2-fold (log₂FC > 1.0) by drought and salt, respectively. Notably, XP_010108435.1 and XP_024022961.1 exhibited leaf-specific high expression and were salt-induced (log₂FC > 1.0); XP_010090405.1 (leaf-specific low) was drought-induced (log₂FC > 1.0); and XP_024023462.1 (root-specific high) was induced by both stresses. These results provide a basis for functional studies and genetic improvement of stress tolerance in mulberry.