Functional Analysis of Glucose-6-Phosphate Translocator PoGPT1 in Embryogenic Callus Formation of Tree Peony

Tree peony (Paeonia ostii) is an ornamental flowering plant that is generally recalcitrant to establishment of a mature somatic embryo regeneration system in vitro. Glucose-6-phosphate translocator (GPT) plays an important regulatory role in embryogenesis of plants. In this study, PoGPT1 was cloned, and a bioinformatic analysis and functional verification of the gene were performed. The results showed that PoGPT1 encoded a polypeptide of 392 amino acids, which was a basic non-secreted hydrophobic transmembrane protein, and was mainly localized in the plastids. PoGPT1 was highly expressed in tree peony leaves, and its transcript abundance increased with the progression of zygotic embryo development. Overexpression of PoGPT1 caused up-regulation of leafy cotyledon 1 (PoLEC1), somatic embryogenesis receptor-like kinase (PoSERK), and agamous-like15 (PoAGL15) in tree peony callus. In addition, PoGPT1 overexpression promoted the increase in indole-3-acetic acid (IAA), 5-deoxystrigol (5DS), and brassinolide (BL) contents, especially of IAA, but reduced the contents of abscisic acid (ABA), 6-benzyladenosine (BARP), and 1-aminocyclopropanecarboxylic acid (ACC). The present research showed that PoGPT1 synergistically regulated the contents of endogenous hormones and expression levels of embryogenesis-related genes to promote the embryonic development of tree peony. The results provide theoretical and technical support for the establishment of a tree peony embryogenic callus formation and subsequent research on somatic embryogenesis.