Bioinformatics and Expressions of CsGLP1 and CsGLP2 in Tea Plant

Objective Bioinformatics and expressions of genes related to the germin-like proteins (GLPs) of cupin superfamily, which are diverse and ubique glycoproteins that play a fundamental role in the response of plants to abiotic and biotic stresses, were studied.

Method Two genes of GLPs, CsGLP1 and CsGLP2, selected from our previous transcriptome data on Acaphylla theae-infected tea plants were analyzed for the physicochemical properties, modification, subcellular localization, structure, promoter sequence, and amino acid sequence of the proteins. Secondary and tertiary structures, evolutionary tree, and expressions in tissues under stresses of the genes were determined.

Result The open reading frame of CsGLP1 was 756 bp encoding 251 amino acids with a molecular weight of 28.68 kD and an isoelectric point of 5.195, while that of CsGLP2 was 606 bp encoding 201 amino acids with a molecular weight of 21.05 kD and an isoelectric point of 8.316. Significant differences in amino acid composition were found between the two proteins. Both genes were subject to modifications such as phosphorylation and glycosylation. The signal peptide sites on them were secretory proteins that were highly conserved on Box A (qDFCVAD), Box B (G--P-H-HpraTexxx--G), and Box C (GXXHFQ-N-G) with sequences highly similar to those of homologous proteins in other plants. With phylogenetic trees belonging to different subfamilies, the genes had secondary structures largely random coils, and tertiary typical homohexamers. The promoters of CsGLP1 and CsGLP2 contained various cis-elements relating to stress response. The gene expressions were tissue-specific and significantly up-regulated by invasion of Ectropis obliqua.

Conclusion CsGLP1 and CsGLP2 in tea plants were identified and analyzed bioinformatically to reveal the different functions in response to pathogenic attacks at different stages. The differentiated gene expressions under 3 artificially imposed biotic stresses led to the speculation of an important role CsGLP2 might play for tea plant in response to the invasion of stinging insects.