Dataset Information

PtiCYP85A3, a BR C-6 Oxidase Gene, Plays a Critical Role in Brassinosteroid-Mediated Tension Wood Formation in Poplar.

ABSTRACT: In angiosperm trees, the gelatinous layer (G-layer) takes a great part of the fiber cell wall in the tension wood (TW). However, the mechanism underlying G-layer formation in poplar is largely unknown. In this work, we demonstrate that G-layer formation in poplar TW cells is regulated by brassinosteroid (BR) and its signaling. PtiCYP85A3, a key BR biosynthesis gene, was predominantly expressed in the xylem of TW, accompanied with a relatively higher castasterone (CS) accumulation, than in the xylem of opposite wood (OW). A wider expression zone of BZR1, a key transcriptional factor in BR singling pathway, was also observed in G-fiber cells on TW side than in wood fiber cells on the OW side, as indicated by immunohistochemistry assays. Transgenic poplar plants overexpressing PtiCYP85A3 produced thicker G-layer with higher cellulose proportion, and accumulated more BZR1 protein in the xylem of TW than did the wild type (WT) plants. Expression of most TW-associated CesAs, which were induced by 2, 4-epibrassinolide, an active BR, and inhibited by brassinazole, a BR biosynthesis inhibitor, were also up-regulated in the xylem of TW in transgenic plants compared to that in WT plants. Further studies with dual-luciferase assays demonstrated that the promoters of PtiCesAs were activated by PtiMYB128, a TW specific transcription factor, which was then regulated by BZR1. All these results indicate that BR plays a crucial role in the G-layer formation of TW fiber cells by regulating the expression of BZR1, PtiMYB128, and PtiCesAs in poplar.

SUBMITTER: Jin Y

PROVIDER: S-EPMC7193022 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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<i>PtiCYP85A3</i>, a BR C-6 Oxidase Gene, Plays a Critical Role in Brassinosteroid-Mediated Tension Wood Formation in Poplar.

Jin Yanli Y Yu Chunyan C Jiang Chunmei C Guo Xiaotong X Li Bei B Wang Cuiting C Kong Fanjing F Zhang Hongxia H Wang Haihai H

Frontiers in plant science 20200424

In angiosperm trees, the gelatinous layer (G-layer) takes a great part of the fiber cell wall in the tension wood (TW). However, the mechanism underlying G-layer formation in poplar is largely unknown. In this work, we demonstrate that G-layer formation in poplar TW cells is regulated by brassinosteroid (BR) and its signaling. <i>PtiCYP85A3</i>, a key BR biosynthesis gene, was predominantly expressed in the xylem of TW, accompanied with a relatively higher castasterone (CS) accumulation, than in ...[more]

PMID: 32391036

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Project description:IntroductionHybrid poplars are industrial trees in China. An understanding of the molecular mechanism underlying wood formation in hybrid poplars is necessary for molecular breeding. Although the division and differentiation of vascular cambial cells is important for secondary growth and wood formation, the regulation of this process is largely unclear.MethodsIn this study, mPagGRF15 OE and PagGRF15-SRDX transgenic poplars were generated to investigate the function of PagGRF15. RNA-seq and qRT-PCR were conducted to analyze genome-wide gene expression, while ChIP‒seq and ChIP-PCR were used to identified the downstream genes regulated by PagGRF15.Results and discussionWe report that PagGRF15 from hybrid poplar (Populus alba × P. glandulosa), a growth-regulating factor, plays a critical role in the regulation of vascular cambium activity. PagGRF15 was expressed predominantly in the cambial zone of vascular tissue. Overexpression of mPagGRF15 (the mutated version of GRF15 in the miR396 target sequence) in Populus led to decreased plant height and internode number. Further stem cross sections showed that the mPagGRF15 OE plants exhibited significant changes in vascular pattern with an increase in xylem and a reduction in phloem. In addition, cambium cell files were decreased in the mPagGRF15 OE plants. However, dominant suppression of the downstream genes of PagGRF15 using PagGRF15-SRDX showed an opposite phenotype. Based on the RNA-seq and ChIP-seq results, combining qRT-PCR and ChIP-PCR analysis, candidate genes, such as WOX4b, PXY and GID1.3, were obtained and found to be mainly involved in cambial activity and xylem differentiation. Accordingly, we speculated that PagGRF15 functions as a positive regulator mediating xylem differentiation by repressing the expression of the WOX4a and PXY genes to set the pace of cambial activity. In contrast, PagGRF15 mediated the GA signaling pathway by upregulating GID1.3 expression to stimulate xylem differentiation. This study provides valuable information for further studies on vascular cambium differentiation mechanisms and genetic improvement of the specific gravity of wood in hybrid poplars.

Dataset Information

PtiCYP85A3, a BR C-6 Oxidase Gene, Plays a Critical Role in Brassinosteroid-Mediated Tension Wood Formation in Poplar.

Publications

<i>PtiCYP85A3</i>, a BR C-6 Oxidase Gene, Plays a Critical Role in Brassinosteroid-Mediated Tension Wood Formation in Poplar.

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