Identification of DELLA Genes and Key Stage for GA Sensitivity in Bolting and Flowering of Flowering Chinese Cabbage.

Hongling Guan,Yanwei Hao,Riyuan Chen,Shiwei Song,Houcheng Liu,Xinmin Huang,Yunna Zhu,Baoxing Xie

doi:10.3390/ijms222212092

Abstract

Flowering Chinese cabbage (Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee) is an important and extensively cultivated vegetable in south China, and its stalk development is mainly regulated by gibberellin (GA). DELLA proteins negatively regulate GA signal transduction and may play an important role in determining bolting and flowering. Nevertheless, no systematic study of the DELLA gene family has been undertaken in flowering Chinese cabbage. In the present study, we found that the two-true-leaf spraying of gibberellin A3 (GA3) did not promote bolting but did promote flowering, whereas the three-true-leaf spraying of GA3 promoted both bolting and flowering. In addition, we identified five DELLA genes in flowering Chinese cabbage. All five proteins contained DELLA, VHYNP, VHIID, and SAW conserved domains. Protein-protein interaction results showed that in the presence of GA3, all five DELLA proteins interacted with BcGID1b (GA-INSENSITIVE DWARF 1b) but not with BcGID1a (GA-INSENSITIVE DWARF 1a) or BcGID1c (GA-INSENSITIVE DWARF 1c). Their expression analysis showed that the DELLA genes exhibited tissue-specific expression, and their reversible expression profiles responded to exogenous GA3 depending on the treatment stage. We also found that the DELLA genes showed distinct expression patterns in the two varieties of flowering Chinese cabbage. BcRGL1 may play a major role in the early bud differentiation process of different varieties, affecting bolting and flowering. Taken together, these results provide a theoretical basis for further dissecting the DELLA regulatory mechanism in the bolting and flowering of flowering Chinese cabbage.

Highlights

After the two-true-leaf stage treatment, there was no significant difference in stem diameter between the gibberellin A3 (GA3) -treated and non-treated plants, whereas for the three-true leaf stage, the stem diameter of the GA3 -treated plants was thinner than that of the control
GA3 treatment had the same effect on the bolting and flowering of flowering Chinese cabbage, accelerating both bolting and flowering time regardless of the treatment stage (Figure 1)
The results showed that BcRGA1, BcRGA2, BcRGL1, BcRGL2, and BcRGL3 interacted with the GID1A, GID1B, GID1C, PIF3, and SLY1 proteins (Figure S1B)

Summary

Introduction

Flowering Chinese cabbage is a subspecies of Chinese cabbage that originated in south China. It is planted throughout the country owing to the increasing consumer demand [1]. The major food product of flowering Chinese cabbage is the stalk, the development of which is directly related to plant quality and yield [2]. Stem elongation, thickening, and flowering are key characteristics of flowering Chinese cabbage stem development. Factors that affect the timing of the bolting and flowering of flowering Chinese cabbage include temperature and plant hormones [3,4,5]. Low temperature and exogenous gibberellin A3 (GA3 ) treatment advance bolting time, stem elongation, and flowering time

Methods

Results

Discussion

Conclusion