Genome-wide investigation of the PLD gene family in alfalfa (Medicago sativa L.): identification, analysis and expression.

Background: External environmental factors, such as salt, alkali and drought, severely limit the acreage and yield of alfalfa. The mining of tolerance-related genes in alfalfa and improving the stress resistance of this plant are essential for increasing alfalfa yield. PLD is the main phospholipid hydrolase in plants and plays an important role in plant growth, development, signaling, and resistance to adverse stress. With the availability of whole genome sequences, the annotation and expression of PLDs in alfalfa can now be achieved. At present, few studies have investigated PLDs in alfalfa. Here, we conducted a study of PLDs in alfalfa and identified and analyzed the expression pattern of PLDs under different treatments.

Results: Fifty-nine MsPLDs were identified in alfalfa and classified into six subtypes: MsPLDα, β, γ, δ and ε belong to the C2-PLD subfamily, and MsPLDζ belongs to the PXPH-PLD subfamily. Members of the same PLD subtype have similar physicochemical properties, sequence structure and domains, but their cis-acting elements are different. A qRT-PCR analysis revealed that MsPLDs are expressed in multiple tissues. MsPLDs can respond to alkali, drought, ABA, IAA, and GA3 treatments and particularly to salt stress. Different expression patterns were found for the same gene under different treatments and different genes under the same treatment. Expression of MsPLD05 improved salt tolerance in yeast.

Conclusion: This study represents the first genome-wide characterization of MsPLDs in alfalfa. Most MsPLDs are expressed mainly in mature leaves and respond positively to abiotic stresses and hormonal treatments. This study further expands the resistance gene pool in legume forage grasses and provides a reference for further in-depth study of MsPLDs in alfalfa.