Identification of BcARR Genes and CTK Effects on Stalk Development of Flowering Chinese Cabbage

Abstract

Flowering Chinese cabbage (Brassica campestris L. ssp. Chinensis var. utilis Tsen et Lee) is an important and extensively cultivated vegetable in south China, whose major food product is the stalk. In the process of stalk formation, its initiation and development are regulated by a series of hormonal signals, such as cytokinin and gibberellin. In this study, we analyzed the effects of zeatin (ZT) and gibberellin A3 (GA3), and their interaction, on the bolting of flowering Chinese cabbage. The results indicated that the three-true-leaf spraying of ZT and GA synthesis inhibitor (PAC) inhibited plant height but increased stem diameter. Cytokinin (CTK) synthesis inhibitor (YZJ) and GA3 treatment increased plant height and decreased stem diameter. In addition, ZT and GA3 co-treated plants displayed antagonistic effect. Further, 19 type-B authentic response regulators (ARR-Bs), the positive regulators of cytokinin signal transduction were identified from flowering Chinese cabbage. Comprehensive analysis of phylogeny showed BcARR-Bs clustered into three subfamilies with 10 conserved motifs. Analysis of their expression patterns in different tissues and at various growth stage, and their response to hormone treatment suggest that ARR1-b localized in the nucleus displayed unique highest expression patterns in stem tips, are responsive both to ZT and GA, suggesting a significant role in mediating the crosstalk of ZT and GA in the bolting of flowering Chinese cabbage.

Transcriptomic analysis of succulent stem development of Chinese kale (Brassica oleracea var. alboglabra Bailey) and its synthetic allotetraploid via RNA sequencing

“…In Brassica campestris , CTK may affect bolting by affecting myeloid cell size and cell cycle gene expression levels to reduce plant height and increase stem diameter. Five key genes ( ARR1-B , ARR2-A , ARR10 , ARR12 and ARR14 ) are highly expressed in different tissues at eight stages ( Ou et al., 2022 ). Studies have found that the number of potato tubers increases during CTK accumulation while individual tuber weight decreases ( Tao et al., 2010 ).…”

“…The genetic mechanism and regulation of succulent stem formation in Chinese kale is still unclear. Therefore, the genetic mechanism of stem formation of Chinese kale and its hybrids could reference from that of storage organ formation in other crops, e.g., potato tubers ( Kondhare et al., 2020 ; Kolachevskaya et al, 2021 ; Kondhare et al., 2021 ; Saidi and Hajibarat, 2021 ), radish taproot ( Yu et al., 2016 ; Xie et al., 2018 ; Xie et al., 2020 ), sweetpotato tuberous root ( Zierer et al., 2021 ), lotus rhizomes ( Yang et al., 2015 ), the bolting stem of flowering Chinese cabbage ( Huang et al., 2017 ; Kou et al., 2021 ; Ou et al., 2022 ), etc.…”

“…Chinensis var. utilis Tsen et Lee), application of exogenous CTK can promote stem thickening and inhibit stem elongation and identified 19 positive regulators of CTK signal transduction type B true response regulators (ARR-BS) ( Ou et al., 2022 ). The predominantly studied bioactive form of AUX is indole-3-acetic acid (IAA) ( Emenecker and Strader, 2020 ).…”

Genome-wide identification of the KNOTTED HOMEOBOX gene family and their involvement in stalk development in flowering Chinese cabbage

“…Previous studies have shown that overexpression of POTH1 (potato homeobox 1) results in lower levels of GA20ox1 (a key rate-limiting enzyme in the synthesis of GA) transcription ( Rosin et al., 2003 ) Moreover, in Arabidopsis , GA3ox1 (GA-biosynthesis gene) transcript shows no difference in KNOX1-overexpression plants ( Hay et al., 2002 ), indicating that GA20ox1 is a specific target in the GA-biosynthesis pathway for KNOX proteins. Several recent studies have revealed that gibberellin and cytokinin play vital roles throughout bolting and flowering ( Guan et al., 2021 ; Ou et al., 2022 ). Meanwhile, our preliminary results indicated that GA and cytokinin exert antagonistic effect on bolting in flowering Chinese cabbage ( Ou et al., 2022 ).…”

“…Several recent studies have revealed that gibberellin and cytokinin play vital roles throughout bolting and flowering ( Guan et al., 2021 ; Ou et al., 2022 ). Meanwhile, our preliminary results indicated that GA and cytokinin exert antagonistic effect on bolting in flowering Chinese cabbage ( Ou et al., 2022 ). We may speculate that BcKNOX family have significant functions in bolting and flowering of flowering Chinese cabbage yet to be discovered.…”