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.

Alkaline stress severely limits plant growth and yield worldwide. NF-YC transcription factors (TFs) respond to abiotic stress by activating gene expression. However, the biological function of NF-YC TFs in alfalfa (Medicago sativa L.) is not clear. In our study, an NF-YC2 gene was identified and transgenic plants were obtained by constructing overexpression vector and cotyledon node transformation system in alfalfa. The open reading frame of MsNF-YC2 is 879 bp with 32.4 kDa molecular mass. MsNF-YC2 showed tissue expression specificity and was induced by a variety of abiotic stresses including drought, salt, and alkali stress in alfalfa. Under alkali stress treatment, transgenic plants exhibited higher levels of antioxidant enzyme activities and proline (Pro), correlating with a lower levels of hydrogen peroxide (H2O2), superoxide anion (O2–) compared with wild-type (WT) plants. Transcriptomic results showed that overexpression of MsNF-YC2 regulated the expression of phytohormone signal transduction and photosynthesis-related genes under normal and alkaline stress treatments. These results suggest that the MsNF-YC2 gene plays crucial role enhance alkali adaptation abilities in alfalfa.

Common vetch (Vicia sativa L.) is an annual herb with high nutritional value, strong adaptability and cold tolerance. It is one of the forage varieties widely planted in the construction of artificial grassland in Qinghai Tibet Plateau. In order to reveal the molecular regulation mechanism of common vetch introduced into plain, physiological and transcriptome analysis of common vetch seedlings in Plateau and plain environment were carried out. In the plain environment, the leaf structure and some physiological indexes of common vetch can adapt to the plain environment gradually and keep stable. However, the maximum photochemical quantum yield (fv/fm) and chlorophyll content (Chl) of PSII fluctuated and could not keep stable. Further transcriptome sequencing showed that there were many different genes involved in photosynthesis pathway, photosynthetic antenna protein pathway, carbon dioxide fixation pathway in photosynthetic organisms and porphyrin and chlorophyll metabolism pathway in plain environment. Similarly, TF analysis showed that MYB, NAC, AP2-EREBP and Orphans were the main transcription factors involved in the adaptation of common vetch to the changes of plain environment. These results may explain that the main reason why the common vetch is not suitable for the plain environment is the difference of the light intensity between the plain and the plateau. These findings provide a theoretical basis for scientific introduction and breeding of new varieties from plateau to plain.