Genome-Wide Analysis and Profile of UDP-Glycosyltransferases Family in Alfalfa (Medicago sativa L.) under Drought Stress

Abstract

Drought stress is one of the major constraints that decreases global crop productivity. Alfalfa, planted mainly in arid and semi-arid areas, is of crucial importance in sustaining the agricultural system. The family 1 UDP-glycosyltransferases (UGT) is indispensable because it takes part in the regulation of plant growth and stress resistance. However, a comprehensive insight into the participation of the UGT family in adaptation of alfalfa to drought environments is lacking. In the present study, a genome-wide analysis and profiling of the UGT in alfalfa were carried out. A total of 409 UGT genes in alfalfa (MsUGT) were identified and they are clustered into 13 groups. The expression pattern of MsUGT genes were analyzed by RNA-seq data in six tissues and under different stresses. The quantitative real-time PCR verification genes suggested the distinct role of the MsUGT genes under different drought stresses and abscisic acid (ABA) treatment. Furthermore, the function of MsUGT003 and MsUGT024, which were upregulated under drought stress and ABA treatment, were characterized by heterologous expression in yeast. Taken together, this study comprehensively analyzed the UGT gene family in alfalfa for the first time and provided useful information for improving drought tolerance and in molecular breeding of alfalfa.

Keywords: Medicago sativa L.; UDP-glycosyltransferases; drought stress response.

Figure 1

Phylogenetic tree of UGTs from alfalfa, A. thaliana and M. truncatula. 17 A. thaliana UGTs members and 14 M. truncatula and 409 identified UGTs from alfalfa were contracted the phylogenetic trees using the MEGA 7 program. These members were clustered into 17 groups (A–N, and O, P, R), and indicated by different colors.

Figure 2

The physical location of MsUGT genes across the 32 chromosomes in the alfalfa genome. These genes were named MsUGT001 to MsUGT409 according to the physical distribution on the chromosomes. The orange bars represent 32 chromosomes, and the position of each MsUGT gene is indicated by the black lines.

Figure 3

Synteny analysis of the UGT genes of alfalfa. Chromosomes are shown in the outer circle in green. Eight different color lines inside indicate duplicated MsUGT gene pairs in 8 chromosomes.

Figure 4

Expression profile of MsUGT genes in six different tissues (flower, nodule, root, leaf, elongating stem internodes, post−elongation stem internodes). The data were retrieved from transcriptome datasets. The heatmap was constructed by TBtools software (v1.098745, Chen, C. J., Guangzhou, China) and expression values (FPKM) were normalized.

Figure 5

The relative water content of leaves under PEG induced drought stress and ABA treatments. CK, MD, SD and ABA represent the control condition, mild and severe drought and ABA treatments, respectively. The error bars indicated the standard errors of three biological replicates. Lowercase letters indicate significant differences.

Figure 6

qRT-PCR results of the relative expression of twelve selected MsUGT genes in response to drought stress and ABA treatment in shoot and root. CK, MD, SD and ABA represent the control condition, mild and severe drought and ABA treatments, respectively. Asterisks indicate the significance compared with CK; * represents significant (p < 0.05) and ** represent highly significant (p < 0.01). The error bars indicate the standard errors of three biological replicates.

Figure 7

Drought stress tolerance and ABA treatment analysis of MsUGT003 and MsUGT024 genes in heterologous expression in yeast with the comparation of empty pYES2 (control) line. The serial dilutions (10⁰, 10¹, 10², 10³ 10⁴, 10⁵, 10⁶) of yeast cultured under control, 30% PEG or 50 μM ABA conditions were spotted onto solid medium containing SC−Ura.