KNOX genes: versatile regulators of plant development and diversity

Hay, Angela; Tsiantis, Miltos

doi:10.1242/dev.030049

Cited by 495 publications

(491 citation statements)

References 104 publications

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“…These observations support a model whereby KNOX accumulation specifies the proximal sheath compartment of very young primordia, and auxin restricts KNOX protein accumulation from distal leaf domains (Bolduc et al, 2012a). Such antagonism between auxin and KNOX is a module that acts in multiple contexts during plant development (Scanlon, 2003;Gallavotti et al, 2008;Hay and Tsiantis, 2010).…”

Section: Introductionsupporting

confidence: 69%

Transcriptomic Analyses Indicate That Maize Ligule Development Recapitulates Gene Expression Patterns That Occur during Lateral Organ Initiation

et al. 2014

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Development of multicellular organisms proceeds via the correct interpretation of positional information to establish boundaries that separate developmental fields with distinct identities. The maize (Zea mays) leaf is an ideal system to study plant morphogenesis as it is subdivided into a proximal sheath and a distal blade, each with distinct developmental patterning. Specialized ligule and auricle structures form at the blade-sheath boundary. The auricles act as a hinge, allowing the leaf blade to project at an angle from the stem, while the ligule comprises an epidermally derived fringe. Recessive liguleless1 mutants lack ligules and auricles and have upright leaves. We used laser microdissection and RNA sequencing to identify genes that are differentially expressed in discrete cell/tissue-specific domains along the proximal-distal axis of wild-type leaf primordia undergoing ligule initiation and compared transcript accumulation in wild-type and liguleless1-R mutant leaf primordia. We identified transcripts that are specifically upregulated at the blade-sheath boundary. A surprising number of these "ligule genes" have also been shown to function during leaf initiation or lateral branching and intersect multiple hormonal signaling pathways. We propose that genetic modules utilized in leaf and/or branch initiation are redeployed to regulate ligule outgrowth from leaf primordia.

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Section: Introductionsupporting

confidence: 69%

Transcriptomic Analyses Indicate That Maize Ligule Development Recapitulates Gene Expression Patterns That Occur during Lateral Organ Initiation

et al. 2014

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“…As the role of KNOX genes in plant development is conserved between dicots and monocots (Hay and Tsiantis, 2010), the reported BOP1/2-dependent KNOX gene regulation in Arabidopsis could indicate similar activity in monocots. As an example, mutations in HvKNOX3 lead to the Hooded phenotype in barley, where an extra floret is formed on the lemma at the transition zone between the leafy part and the awn (Müller et al, 1995).…”

Section: Hvlax-a a Key Regulatory Gene Of Barley Inflorescence Archimentioning

confidence: 99%

A homolog of Blade-On-Petiole 1 and 2 (BOP1/2) controls internode length and homeotic changes of the barley inflorescence

et al. 2016

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Inflorescence architecture in small-grain cereals has a direct effect on yield and is an important selection target in breeding for yield improvement. We analyzed the recessive mutation laxatum-a (lax-a) in barley (Hordeum vulgare), which causes pleiotropic changes in spike development, resulting in (1) extended rachis internodes conferring a more relaxed inflorescence, (2) broadened base of the lemma awns, (3) thinner grains that are largely exposed due to reduced marginal growth of the palea and lemma, and (4) and homeotic conversion of lodicules into two stamenoid structures. Map-based cloning enforced by mapping-by-sequencing of the mutant lax-a locus enabled the identification of a homolog of BLADE-ON-PETIOLE1 (BOP1) and BOP2 as the causal gene. Interestingly, the recently identified barley uniculme4 gene also is a BOP1/2 homolog and has been shown to regulate tillering and leaf sheath development. While the Arabidopsis (Arabidopsis thaliana) BOP1 and BOP2 genes act redundantly, the barley genes contribute independent effects in specifying the developmental growth of vegetative and reproductive organs, respectively. Analysis of natural genetic diversity revealed strikingly different haplotype diversity for the two paralogous barley genes, likely affected by the respective genomic environments, since no indication for an active selection process was detected.The inflorescence is the most prominent part of smallgrain cereal plants, producing the carbohydrate-rich grains that are harvested for food, feed, and fiber. However, our understanding of the genetic factors that regulate inflorescence architecture remains limited. What is clear is that the appearance and shape of the inflorescence has been under constant visual selection since early domestication and is still ongoing in modern plant breeding due to the impact of inflorescence architecture on crop yield. For instance, in barley (Hordeum vulgare), strong selection has been exerted on spontaneously occurring alleles of nonbrittle rachis1 (btr1) and btr2 that prevent dehiscence of the rachis at maturity (Pourkheirandish et al., 2015), six-rowed spike1 (vrs1) that determines whether the inflorescence exhibits two or six rows of grain (Komatsuda et al., 2007), and nudum (nud) that controls whether the grain is hulled or hull-less (Taketa et al., 2008). Ultimately, knowing all of the genes that control cereal inflorescence architecture will provide targets for understanding and exploiting natural or induced genetic diversity toward improving both yield potential and end-use characteristics.The barley inflorescence or spike forms an unbranched main rachis carrying triplets of sessile single-floreted

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“…BELL and KNOX proteins are three-amino acid-loopextension (TALE) superclass transcription factors; the tandem complex of BELL and KNOX regulates the expression of target genes in developmental processes (Chen et al, 2003;Kanrar et al, 2006;Hay and Tsiantis, 2010). Interactions between BELL and KNOX proteins have been observed in barley (Hordeum vulgare; Müller et al, 2001), Arabidopsis (Arabidopsis thaliana; Smith and Hake, 2003), maize (Zea mays; Smith et al, 2002), and potato (Solanum tuberosum; Chen et al, 2003).…”

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confidence: 99%

KNOX Protein OSH15 Induces Grain Shattering by Repressing Lignin Biosynthesis Genes

et al. 2017

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Seed shattering is an agronomically important trait. Two major domestication factors are responsible for this: qSH1 and SH5. Whereas qSH1 functions in cell differentiation in the abscission zone (AZ), a major role of SH5 is the repression of lignin deposition. We have determined that a KNOX protein, OSH15, also controls seed shattering. Knockdown mutations of OSH15 showed reduced seed-shattering phenotypes. Coimmunoprecipitation experiments revealed that OSH15 interacts with SH5 and qSH1, two proteins in the BELL homeobox family. In transgenic plants carrying the OSH15 promoter-GUS reporter construct, the reporter gene was preferentially expressed in the AZ during young spikelet development. The RNA in situ hybridization experiment also showed that OSH15 messenger RNAs were abundant in the AZ during spikelet development. Analyses of osh15 SH5-D double mutants showed that SH5 could not increase the degree of seed shattering when OSH15 was absent, indicating that SH5 functions together with OSH15. In addition to the seedshattering phenotype, osh15 mutants displayed dwarfism and accumulated a higher amount of lignin in internodes due to increased expression of the genes involved in lignin biosynthesis. Knockout mutations of CAD2, which encodes an enzyme for the last step in the monolignol biosynthesis pathway, caused an easy seed-shattering phenotype by reducing lignin deposition in the AZ. This indicated that the lignin level is an important determinant of seed shattering in rice (Oryza sativa). Chromatin immunoprecipitation assays demonstrated that both OSH15 and SH5 interact directly with CAD2 chromatin. We conclude that OSH15 and SH5 form a dimer that enhances seed shattering by directly inhibiting lignin biosynthesis genes.

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KNOX genes: versatile regulators of plant development and diversity

Cited by 495 publications

References 104 publications

Transcriptomic Analyses Indicate That Maize Ligule Development Recapitulates Gene Expression Patterns That Occur during Lateral Organ Initiation

Transcriptomic Analyses Indicate That Maize Ligule Development Recapitulates Gene Expression Patterns That Occur during Lateral Organ Initiation

A homolog of Blade-On-Petiole 1 and 2 (BOP1/2) controls internode length and homeotic changes of the barley inflorescence

KNOX Protein OSH15 Induces Grain Shattering by Repressing Lignin Biosynthesis Genes

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