Cloning of GbAGL15 and GbAIL5 from Gossypium barbadense and Its Expression during Synchronization of XH16 Somatic Embryogenesis Induced by Low Temperature
Abstract：Synchronization of somatic embryogenesis helps accelerate the process of crop molecular breeding. The specific expression of key genes such as Agamous-like15 (AGL15) and Aintegumenta-like5 (AIL5) plays a role similar to switch during somatic embryogenesis. To further explore the molecular mechanism of hypothermia induced somatic embryo synchronization, in this study, GbAGL15 (GenBank No. MK580460) and GbAIL5 (GenBank No. MK591943) were cloned by homologous sequences methods from the embryonic callus of Gossypium barbadense XH16, and the expression pattern of GbAGL15 and GbAIL5 genes in low temperature treated embryogenic cells were checked by qRT-PCR. The results showed that the coding region of GbAGL15 gene was 753 bp and encoded 250 amino acids, which contained the MADS-MEF2-like domain and the K-box conserved region. Phylogenetic tree analysis showed that there was a close relationship among GbAGL15 together with GrAGL15 (G. raimondii) and GaAGL15 (G. arboretum). The coding region of GbAIL5 gene was 1 626 bp and encoded 541 amino acid in the coding segment, and it contained two AP2 domains. Phylogenetic tree analysis showed that GbAIL5 was located in the same evolutionary branch with GhAIL5 (G. hirsutum). qRT-PCR results showed that the expression levels of GbAGL15 and GbAIL5 in embryogenic callus were significantly lower than those of the control group after low temperature treatment. It was speculated that the GbAGL15 and GbAIL5 genes might be involved in somatic embryogenesis and played regulatory roles. Under low temperature conditions, the two gene expression might be inhibited, resulting in the development and differentiation of hypocotyl callus tissue at low temperature, which might promotes the synchronization of somatic embryos. And after the stress conditions were removed, the embryo development could be swithced on in synchronization pattern. The study partially elucidates the mechanism of hypothermia induced somatic embryo synchronization, promoting the foundation of high efficient system of somatic embryogenesis-dependent genetic transformation in G. barbadense.
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