Genome-wide identification of xyloglucan endotransglucosylase/hydrolase gene family members in peanut and their expression profiles during seed germination.

Seed germination marks the beginning of a new plant life cycle. Improving the germination rate of seeds and the consistency of seedling emergence in the field could improve crop yields. Many genes are involved in the regulation of seed germination. Our previous study found that some peanut (xyloglucan endotransglucosylases/hydrolases) were expressed at higher levels at the newly germinated stage. However, studies of the XTH gene family in peanut have not been reported. In this study, a total of 58 genes were identified in the peanut genome. Phylogenetic analysis showed that these , along with 33 from Arabidopsis and 61 from soybean, were classified into three subgroups: the I/II, IIIA and IIIB subclades. All genes were unevenly distributed on the 18 peanut chromosomes, with the exception of chr. 07 and 17, and they had relatively conserved exon-intron patterns, most with three to four introns. Through chromosomal distribution pattern and synteny analysis, it was found that the family experienced many replication events, including 42 pairs of segmental duplications and 23 pairs of tandem duplications, during genome evolution. Conserved motif analysis indicated that their encoded proteins contained the conserved ExDxE domain and N-linked glycosylation sites and displayed the conserved secondary structural loops 1-3 in members of the same group. Expression profile analysis of freshly harvested seeds, dried seeds, and newly germinated seeds using transcriptome data revealed that 26 genes, which account for 45% of the gene family, had relatively higher expression levels at the seed germination stage, implying the important roles of in regulating seed germination. The results of quantitative real-time PCR also confirmed that some were upregulated during seed germination. The results of GUS histochemical staining showed that was mainly expressed in germinated seeds and etiolated seedlings and had higher expression levels in elongated hypocotyls. was also verified to play a crucial role in the cell elongation of hypocotyls during seed germination.