Brassinosteroid Regulates Root Development with Highly Redundant Genes in Hexaploid Wheat

Abstract

Brassinosteroid (BR) plays an important role in plant development and biotic and abiotic stress tolerance, but its specific function remains largely unknown in wheat (Triticum aestivum L.), preventing its utilization in this important crop. In this study, the function of BR and its underlying cytological role in wheat root development were comprehensively investigated. Our findings demonstrated that BR has a conserved function in regulating root length in wheat, and novel roles in regulating lateral root emergence and root diameter were uncovered. Analyses of BR homologous gene composition and evolutionary divergence demonstrated that the genetic framework of the wheat BR pathway was close to that of rice, but contained highly redundant homologous copies of genes from the subgenome A, B and D. These homologous copies showed active expression and shared a conserved BR response. The expression of wheat DWF4 and glycogen synthase kinase (GSK) genes in Arabidopsis confirmed that multiple homologous copies maintained their conserved function in regulating root development, highlighting their redundant status and indicating that a special challenge exists in wheat gene modification to deal with this high redundancy. However, our results suggested that the hypermorphic effect of T. aestivum GSK (TaGSK) genes with point mutations may be an effective approach to overcome this redundancy in the manipulation of BR signaling in wheat. Our study provides fundamental data uncovering the function of BR in wheat root development, the underlying genetic basis and a possible strategy to manipulate BR signaling in hexaploid wheat.

Wheat Type One Protein Phosphatase Participates in the Brassinosteroid Control of Root Growth via Activation of BES1

“…Although BR signaling mechanisms in Arabidopsis and rice are well documented, involvement of PP1s in regulating the BR pathway was not reported before. In wheat, the major BR signaling components are conserved but highly redundant, with each component having one copy per subgenome [ 42 ]. Therefore, uncovering this novel role of PP1s on BES1 activation would have been difficult in polyploid wheat.…”

Genome-wide Identification of Gramineae Histone Modification Genes and their Potential Roles in Regulating Wheat and Maize Growth and Stress Responses

“…In Arabidopsis, rice, wheat and maize, BR has been proved to play important roles in root growths, including lateral root (LR) initiation and hair formation [26][27][28][29]. BR treatment signi cantly increases wheat lateral root number, but inhibits root length and root diameter, and BR synthesis inhibitor BRZ showed opposite roles on lateral root number and root diameter [26]. HMs genes have been known to regulate various developmental processes, while their information in regulating wheat root is absent.…”

“…BR is an essential plant hormone and stimulates wheat root hair formation and LR initiation [26]. However, responses of TaHMs to BR and BRZ were not identi ed.…”

“…Wheat seedlings (3day-old) treated with 50 nM epibrassinolide (EpiBL, Sigma) as BR1 treated group, 1 mM EpiBL as BR2 treated group and 1 mM BRZ (BR synthesis inhibitor, Sigma) as BRZ treated group. After 12 d treatment, wheat roots were sampled and used for RNA-seq analysis [26]. Differentially expressed genes (DEGs) were provided by the corresponding author of published research [26].…”

“…After 12 d treatment, wheat roots were sampled and used for RNA-seq analysis [26]. Differentially expressed genes (DEGs) were provided by the corresponding author of published research [26].…”