Genetic Regulation of GA Metabolism during Vernalization, Floral Bud Initiation and Development in Pak Choi (Brassica rapa ssp. chinensis Makino)

Abstract

Pak choi (Brassica rapa ssp. chinensis Makino) is a representative seed vernalization vegetable and premature bolting in spring can cause significant economic loss. Thus, it is critical to elucidate the mechanism of molecular regulation of vernalization and floral bud initiation to prevent premature bolting. Gibberellin (GA) is the key plant hormone involved in regulating plant development. To gain a better understanding of GA metabolism in pak choi, the content of GA in pak choi was measured at different stages of plant development using enzyme-linked immunosorbent assay. The results showed that the GA content increased significantly after low-temperature treatment (4°C) and then decreased rapidly with vegetative growth. During floral bud initiation, the GA content increased rapidly until it peaked upon floral bud differentiation. To elucidate these changes in GA content, the expression of homologous genes encoding enzymes directly involved in GA metabolism were analyzed. The results showed that the changes in the expression of four genes involved in GA synthesis (Bra035120 encoding ent-kaurene synthase, Bra009868 encoding ent-kaurene oxidase, Bra015394 encoding ent-kaurenoic acid oxidase, and Bra013890 encoding GA20-oxidase) were correlated with the changes in GA content. In addition, by comparing the expression of genes involved in GA metabolism at different growth stages, seven differentially expressed genes (Bra005596, Bra009285, Bra022565, Bra008362, Bra033324, Bra010802, and Bra030500) were identified. The differential expression of these genes were directly correlated with changes in GA content, suggesting that these genes were directly related to vernalization, floral bud initiation and development. These results contribute to the understanding of the molecular mechanism of changes in GA content during different developmental phases in pak choi.

Low Overnight Temperature-Induced Gibberellin Accumulation Increases Locule Number in Tomato

“…GA 1 , GA 4 , and GA 7 were detected at all stages of flower bud differentiation, while GA 3 was detected at pre-flower bud differentiation (Table 3). GA 1 and GA 4 were more sensitive to low overnight temperature than GA 7 , since GA 7 is not the subject of degradation by GA2 oxidases (Table 3) [29], and lower-temperature treatment can increase GAs content during floral bud differentiation, in agreement with a previous report [41].…”

“…GA metabolites show a strong temperature-dependent accumulation during flower bud differentiation in tomato (Figure 4; Table 3). By analyzing the expression profiles of GAs, the changes in the expression of SlGA2ox genes encoding degradation enzymes related to GA metabolism were downregulated significantly after lower-temperature treatment in agreement with a previous report [41]. In order to further elucidate the results of changes in the expression of SlGA2ox genes in tomato after lower overnight temperature treatment, the GA content in tomato was analyzed.…”

Roles of the GA-mediated SPL Gene Family and miR156 in the Floral Development of Chinese Chestnut (Castanea mollissima)

“…To analyze the effects of the exogenous addition of the hormone GA and the GA inhibitor PP 333 on endogenous hormones, the expression levels of key genes in the GA synthesis and signaling pathways were determined (Figure 1B). Three key genes in in the GA synthetic pathway, namely, ent-kaurene synthase ( KS ), ent-kaurene oxidase ( KO ), and ent-kaurenoic acid oxidase ( KAO ), and two typical genes in the GA signaling pathway, namely, DELLA and GA-insensitive drawf1 ( GID1 ), were selected [39]. Their analysis revealed that KS and GID1 gene expression showed a decreasing trend during floral bud differentiation, and no significant difference was obtained after the treatments.…”

Translating Flowering Time from Arabidopsis thaliana to Brassicaceae and Asteraceae Crop Species

“…In B. rapa , low-temperature treatment increases the GA content, and enhanced GA accumulation initiates floral bud differentiation [210]. Expression patterns of most genes involved in GA metabolism, particularly those of four genes including one GA20ox were consistent with observed GA levels [210].…”