Abstract
Germins and germin-like proteins (GLPs) are glycoproteins closely associated with plant development and stress response in the plant kingdom. Here, we carried out genome-wide identification and expression analysis of the GLP gene family in cucumber to study their possible functions. A total of 38 GLP genes were identified in cucumber, which could be mapped to six out of the seven cucumber chromosomes. A phylogenetic analysis of the GLP members from cucumber, Arabidopsis and rice showed that these GLPs could be divided into six groups, and cucumber GLPs in the same group had highly similar conserved motif distribution and gene structure. Gene duplication analysis revealed that six cucumber GLP genes were located in the segmental duplication regions of cucumber chromosomes, while 14 genes were associated with tandem duplications. Tissue expression profiles of cucumber GLP genes showed that many genes were preferentially expressed in specific tissues. In addition, some cucumber GLP genes were differentially expressed under salt, drought and ABA treatments, as well as under DM inoculation. Our results provide important information for the functional identification of GLP genes in the growth, development and stress response of cucumber.
Highlights
Germin was first identified in wheat’s embryos and labeled as a germination marker; it was subsequently characterized as a homohexamer glycoprotein with oxalate oxidase (OXO, EC 1.2.3.4) activity [1,2]
38 candidate germin-like proteins (GLPs) genes were identified in the cucumber genome, which were assigned according to their chromosomal locations (Table 1)
The results revealed that all the sequences had the cupin domain (PF00190), which is the typical configuration of GLP proteins, suggesting that they belong to the GLP gene family
Summary
Germin was first identified in wheat’s embryos and labeled as a germination marker; it was subsequently characterized as a homohexamer glycoprotein with oxalate oxidase (OXO, EC 1.2.3.4) activity [1,2]. Proteins with similar amino acid sequences and structures to wheat germin are defined as germin-like proteins (GLPs) [3,4,5]. GLPs are a type of soluble glycoproteins with a “cupin” domain (PF00190) belonging to the “cupin superfamily”. Besides OXO activity, various other enzymatic activities were found in GLPs, such as superoxide dismutase (SOD, EC 1.15.1.1) [10,11], ADP glucose pyrophosphatase/phosphodiesterase (AGPPase, EC 3.1.4.1) [12], and polyphenol oxidases (PPO) [13,14]
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