Zea mays GSK2 gene is involved in brassinosteroid signaling
2022
Hou, Lijiang | Li, Zheng | Shaheen, Aaqib | Zhang, Kunpeng | Wang, Jingshun | Gao, Xinqiang | Wu, Qiufang
Brassinosteroids (BRs) are plant hormones involved in various growth and developmental processes in plants. The BR signaling system is well established in Arabidopsis but poorly understood in maize (Zea mays L.). BRASSINOSTEROID-INSENSITIVE 2 (BIN2) is a key negative regulator in BR signaling and plays critical roles in regulating plant height, root development, flowering, fertility, grain size, and the whole plant architecture. A search of the maize database and additional phylogenetic analyses identified two candidate genes ZmGSK1 and ZmGSK2 of BIN2 in maize. ZmGSK2 was highly and ubiquitously expressed in maize tissues. Heterologous expression of ZmGSK2 carrying a point mutation in Arabidopsis resulted in a stunted growth phenotype, which could be partially rescued by bikinin, a strong activator of BR signaling. Growth responses of maize roots and aerial parts were affected when seedling roots were treated with epibrassinolide or bikinin. The experimental observations showed that BR significantly reduces the root length in the medium containing 100 nM and 1 µM, while dramatically increases in the presence of 10 nM concentration. The BR inhibition effects were also observed in the seedling’s aerial parts by 100 nM and 1 µM treatment. Bikinin showed the inhibition effect on these two phenotypes roots and aerial part, particularly at higher concentrations 100 nM. Our results suggest that ZmGSK2 is the ortholog of BIN2 and plays a critical role in mediating BR signaling. This study highlights the function of BR pathway key member in maize development and site-directed mutation of ZmGSK2 TREE domain, which extends a strategy to manipulate BR signaling in maize.
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