KNAT7 positively regulates xylan biosynthesis by directly activating <i>IRX9</i> expression in <i>Arabidopsis</i>

He, Jun; Zhao, Xianhai; Du, Pingzhou; Zeng, Wei; Beahan, Cherie T.; Wang, Yuqi; Li, Huiling; Bacic, Antony; Wu, Ai‐Min

doi:10.1111/jipb.12638

Cited by 41 publications

(34 citation statements)

References 69 publications

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“…The rice plants were grown in a greenhouse and cultivated as previously described (Yang et al ., ). Arabidopsis plants were grown at 22°C with 16/8 h (light/dark) photoperiod at approximately 120 μmol m −2 sec −1 light (He et al ., ).…”

Section: Methodsmentioning

confidence: 97%

CRD1, an Xpo1 domain protein, regulates miRNA accumulation and crown root development in rice

Zhu

Lin

et al. 2019

The Plant Journal

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Crown root (CR) is the main component of the fibrous root system in cereal crops, but the molecular mechanism underlying CR development is still unclear. Here, we isolated the crown root defect 1 (crd1) mutant from ethyl methane sulfonate-mutated mutant library, which significantly inhibited CR development. The CRD1 was identified through genome resequencing and complementation analysis, which encodes an Xpo1 domain protein: the rice ortholog of Arabidopsis HASTY (HST) and human exportin-5 (XPO5). CRD1 is ubiquitously expressed, with the highest expression levels in the CR primordium at the stem base. CRD1 is a nucleocytoplasmic protein. The crd1 mutant contains significantly reduced miRNA levels in the cytoplasm and nucleus, suggesting that CRD1 is essential for maintaining normal miRNA levels in plant cells. The altered CR phenotype of crd1 was simulated by target mimicry of miR156, suggesting that this defect is due to the disruption of miR156 regulatory pathways. Our analysis of CRD1, the HST ortholog identified in monocots, expands our understanding of the molecular mechanisms underlying miRNA level and CR development.

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Section: Methodsmentioning

confidence: 97%

CRD1, an Xpo1 domain protein, regulates miRNA accumulation and crown root development in rice

Zhu

Lin

et al. 2019

The Plant Journal

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“…The transcriptional repression by KNAT7 and BLH6 is enhanced by their interaction with other TFs, including OVATE FAMILY PROTEIN (OFP) 1 and 4, during SCW biosynthesis [74,75]. By analyzing different knat7 mutants, KNAT7 was shown to regulate the expression of several xylan biosynthetic genes (IRX8, IRX9, FRA8) either positively [76] or negatively [77]. This result suggests that the xylan and lignin biosynthetic pathways do not share the same regulatory network, despite their common activation by several MYB and NAC TFs [78].…”

Section: Knox Bell and Homeodomain: From Cell Division To Fiber Scwmentioning

confidence: 99%

A Molecular Blueprint of Lignin Repression

Behr¹,

Guerriero²,

Grima‐Pettenati³

et al. 2019

Trends in Plant Science

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Although lignin is essential to ensure the correct growth and development of land plants, it may be an obstacle to the production of lignocellulosics-based biofuels, and reduces the nutritional quality of crops used for human consumption or livestock feed. The need to tailor the lignocellulosic biomass for more efficient biofuel production or for improved plant digestibility has fostered considerable advances in our understanding of the lignin biosynthetic pathway and its regulation. Most of the described regulators are transcriptional activators of lignin biosynthesis, but considerably less attention has been devoted to the repressors of this pathway. We provide a comprehensive overview of the molecular factors that negatively impact on the lignification process at both the transcriptional and post-transcriptional levels. Challenging LigninLignin is a major cell wall component that fulfills fundamental functions in plant development as well as in defense against pests and pathogens. This heteropolymer impregnates the compound middle lamella and the secondary cell walls (SCWs) of cells genetically programmed to be lignified, such as xylem tracheary elements as well as xylem and phloem fibers. Lignin biosynthesis spans the phenylpropanoid and the monolignol pathways, from phenylalanine to p-coumaryl, coniferyl, and sinapyl alcohols. Monolignol homeostasis is regulated through a balance between the molecular factors that antagonistically regulate their biosynthesis. After monolignols are excreted into the apoplast, they are oxidized by the phenol-oxidoreductase laccases and/or by class III peroxidases, and are polymerized by radical coupling. A complex regulatory network involving phytohormones, transcription factors (TFs), and post-transcriptional events guide SCW deposition and lignification [1]. This network prevents lignin deposition in tissues undergoing active division or elongation such as apical meristems, vascular cambium, and immature xylem cells, as well as in non-lignified tissues such as stem pith and flax or hemp bast fibers that harbor gelatinous walls under normal developmental conditions. Similarly, this network negatively regulates lignification in xylem tissue formed in response to mechanical stresses such as, for instance, poplar tension wood that harbors hypolignified gelatinous walls.

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“…Hence, KNAT7 has an unexpected role in controlling cell size. Although previous studies have proposed that the roles of KNAT7 might vary in different tissues and cell types (Li et al, 2012;He et al, 2018), its role in coordinating cell expansion and wall thickening has not yet been found in other plant species.…”

Section: Discussionmentioning

confidence: 95%

“…Although studies in several plant species have revealed that KNAT7 governs secondary wall thickening, its function differs among species. Arabidopsis KNAT7 can repress lignin biosynthesis in the interfascicular fiber cells (Brown et al, 2005;Zhong et al, 2008;Li et al, 2012) and activate xylan production in xylary tissues (He et al, 2018). The mechanism underlying KNAT7 function remains controversial.…”

Section: Discussionmentioning

confidence: 99%

“…This finding places rice KNAT7 in the upstream hierarchy of the secondary wall regulatory network, which is distinct from previous reports. Studies in several plant species have found that KNAT7 can regulate secondary wall formation in various ways (Brown et al, 2005;Li et al, 2012;Gong et al, 2014;He et al, 2018), depending upon its target genes and interacting partners (Li et al, 2012;Zhong and Ye, 2012). The divergent regulatory network for secondary wall biosynthesis among different plant species might be one of the reasons why KNAT7 function varies in different plant species and in specific cell types.…”

Section: Discussionmentioning

confidence: 99%

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Rice Homeobox Protein KNAT7 Integrates the Pathways Regulating Cell Expansion and Wall Stiffness

et al. 2019

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During growth, plant cells must coordinate cell expansion and cell wall reinforcement by integrating distinct regulatory pathways in concert with intrinsic and external cues. However, the mechanism underpinning this integration is unclear, as few of the regulators that orchestrate cell expansion and wall strengthening have been identified. Here, we report a rice (Oryza sativa) Class II KNOX-like homeobox protein, KNOTTED ARABIDOPSIS THALIANA7 (KNAT7), that interacts with different partners to govern cell expansion and wall thickening. A loss-of-function mutation in KNAT7 enhanced wall mechanical strength and cell expansion, resulting in improved lodging resistance and grain size. Overexpression of KNAT7 gave rise to the opposite phenotypes, with plants having weaker cell walls and smaller grains. Biochemical and gene expression analyses revealed that rice KNAT7 interacts with a secondary wall key regulator, NAC31, and a cell growth master regulator, Growth-Regulating Factor 4 (GRF4). The KNAT7-NAC31 and KNAT7-GRF4 modules suppressed regulatory pathways of cell expansion and wall reinforcement, as we show in internode and panicle development. These modules function in sclerenchyma fiber cells and modulate fiber cell length and wall thickness. Hence, our study uncovers a mechanism for the combined control of cell size and wall strengthening, providing a tool to improve lodging resistance and yield in rice production.

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KNAT7 positively regulates xylan biosynthesis by directly activating IRX9 expression in Arabidopsis

Cited by 41 publications

References 69 publications

CRD1, an Xpo1 domain protein, regulates miRNA accumulation and crown root development in rice

CRD1, an Xpo1 domain protein, regulates miRNA accumulation and crown root development in rice

A Molecular Blueprint of Lignin Repression

Rice Homeobox Protein KNAT7 Integrates the Pathways Regulating Cell Expansion and Wall Stiffness

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