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.
Highlights
Pak choi (Brassica rapa ssp. chinensis Makino) is a cruciferous vegetable and is representative plant that require vernalization
The results showed that the expression of Bra000864 encoding copalyl diphosphate synthase (CPS), Bra035120 encoding KS, Bra009868 encoding kaurene oxidase (KO), Bra015394 encoding kaurenoic acid oxidase (KAO), Bra019165 and Bra013890 encoding GA20ox were all upregulated in CK0 vs. V0, V10 vs. V15, and CK16 vs. V16; that is, the gene expression in cold treatment sample were higher than the control after cold treatment and at floral bud differentiation stage 1
The results showed that low-temperature treatment increased the GA content, and enhanced GA accumulation initiated floral bud differentiation
Summary
Pak choi (Brassica rapa ssp. chinensis Makino) is a cruciferous vegetable and is representative plant that require vernalization. Chinensis Makino) is a cruciferous vegetable and is representative plant that require vernalization. After exposure to low temperatures for a period of time, the plant blossoms under high temperatures and long days. It is crucial to study the molecular regulation of vernalization to prevent bolting in pak choi and possibly other cruciferous vegetables. Plant hormones play an important role in vernalization and flowering (Aryal and Ming, 2014). GA can partially replace long-day or low temperature to promote flowering in plants (Pearce and Dubcovsky, 2013; Hu et al, 2016). Treatment with GA has been shown to promote the flowering of pak choi (Hou et al, 2009; Yu et al, 2009). Studying the regulation of GA on flowering in pak choi is important
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
