Abscisic Acid Represses Rice Lamina Joint Inclination by Antagonizing Brassinosteroid Biosynthesis and Signaling

Abstract

Leaf angle is a key parameter that determines plant architecture and crop yield. Hormonal crosstalk involving brassinosteroid (BR) plays an essential role in leaf angle regulation in cereals. In this study, we investigated whether abscisic acid (ABA), an important stress-responsive hormone, co-regulates lamina joint inclination together with BR, and, if so, what the underlying mechanism is. Therefore, lamina joint inclination assay and RNA sequencing (RNA-Seq) analysis were performed here. ABA antagonizes the promotive effect of BR on leaf angle. Hundreds of genes responsive to both hormones that are involved in leaf-angle determination were identified by RNA-Seq and the expression of a gene subset was confirmed using quantitative real-time PCR (qRT-PCR). Results from analysis of rice mutants or transgenic lines affected in BR biosynthesis and signaling indicated that ABA antagonizes the effect of BR on lamina joint inclination by targeting the BR biosynthesis gene D11 and BR signaling genes GSK2 and DLT, thus forming a multi-level regulatory module that controls leaf angle in rice. Taken together, our findings demonstrate that BR and ABA antagonistically regulate lamina joint inclination in rice, thus contributing to the elucidation of the complex hormonal interaction network that optimizes leaf angle in rice.

Exploring the Brassinosteroid Signaling in Monocots Reveals Novel Components of the Pathway and Implications for Plant Breeding

“…Moreover, the BR feedback-mediated inhibition of the OsBRI1 gene expression was partially counteracted by the ABA application. However, the OsGSK2 kinase (partially) and the OsDLT transcription factor (chiefly) constitute the major nodes in the ABA-BR signaling crosstalk and the regulation of leaf inclination [7].…”

“…Thus, the increase in the planting density is considered as a major solution of the global need for enhancement in crop yield on limited arable lands to feed the global population [6]. Leaf angle is one of the key parameters determining cereal crop architecture and yield [7]. Thus, breeding cereals for more erect leaves is a strategy for the crop productivity improvement [8].…”

“…Thus, breeding cereals for more erect leaves is a strategy for the crop productivity improvement [8]. Brassinosteroids (BRs) play a prominent role in hormonal crosstalk which regulates this parameter in cereals [7,[9][10][11]. In the past, application of semi-dwarf cultivars of rice (Oryza sativa) and wheat (Triticum aestivum) which were related mostly with the gibberellin metabolism and the BR signaling-related barley (Hordeum vulgare) mutant 'uzu' has significantly contributed to the yield increase, known as the 'Green Revolution' [12][13][14].…”

Regulation of Brassinosteroid Homeostasis in Higher Plants

“…Moreover, the functional mechanism of JUB1 in regulating BR/GA biosynthesis and signaling is considerably conserved across species ( Shahnejat-Bushehri et al, 2017 ). Jasmonic acid and abscisic acid were found to inhibit the expression of BR biosynthetic genes to antagonize BR functions ( Ren et al, 2009 ; Gan et al, 2015 ; Li et al, 2019 ). Melatonin also plays a role in regulating BR biosynthesis.…”

Evaluation of suitable reference genes for normalization of quantitative real-time PCR analysis in rice plants under Xanthomonas oryzae pv. oryzae--infection and melatonin supplementation

“…For the rest eight candidate genes, the mean Ct values ranged from 7.51 to 28.43 in the water group, from 7.54 to 28.56 in the Xoo group, from 7.36 to 28.36 in the MT-water group, and from 7.25 to 28.94 in the MT-Xoo group Li et al 2019)…”