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A single amino acid replacement in ETC2 shapes trichome patterning in natural Arabidopsis populations.

ABSTRACT: Our understanding of the evolution of organismal diversity is restricted by the current resolution of the genotype-phenotype map. In particular, the genetic basis of environmentally relevant phenotypic variation among natural populations remains poorly understood. Trichomes are single-cell outgrowths on the surface of plant leaves and other above-ground organs. Consistent with trichomes' suggested function to protect plants from predators and abiotic stressors [1-3], trichome density is strikingly variable among natural populations (e.g., [2, 4]). Despite substantial progress in the genetic dissection of trichome development [5], how trichome number is modulated in natural populations remains enigmatic. Here, we show that the ENHANCER OF TRY AND CPC 2 (ETC2) from the single-repeat R3 MYB family is the major locus determining trichome patterning in natural Arabidopsis populations. Our study identifies a single amino acid substitution in ETC2 (K19E) as the causal quantitative trait nucleotide (QTN). We suggest that this amino acid replacement might affect the stability of the ETC2 repressor, which results in a reduced trichome number. This is consistent with the view that morphology can evolve by coding changes that can subtly modulate protein activity as well as cis-regulatory changes that alter expression patterns.

SUBMITTER: Hilscher J

PROVIDER: S-EPMC2864576 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature

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A single amino acid replacement in ETC2 shapes trichome patterning in natural Arabidopsis populations.

Hilscher Julia J Schlötterer Christian C Hauser Marie-Theres MT

Current biology : CB 20091008 20

Our understanding of the evolution of organismal diversity is restricted by the current resolution of the genotype-phenotype map. In particular, the genetic basis of environmentally relevant phenotypic variation among natural populations remains poorly understood. Trichomes are single-cell outgrowths on the surface of plant leaves and other above-ground organs. Consistent with trichomes' suggested function to protect plants from predators and abiotic stressors [1-3], trichome density is striking ...[more]

PMID: 19818620

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Project description:BACKGROUND: Single-repeat R3 MYB transcription factors (single-repeat MYBs) play important roles in controlling trichome patterning in Arabidopsis. It was proposed that single-repeat MYBs negatively regulate trichome formation by competing with GLABRA1 (GL1) for binding GLABRA3/ENHANCER OF GLABRA3 (GL3/EGL3), thus inhibiting the formation of activator complex TTG1(TRANSPARENT TESTA GLABRA1)-GL3/EGL3-GL1 that is required for the activation of GLABRA2 (GL2), whose product is a positive regulator of trichome formation. Previously we identified a novel single-repeat MYB transcription factor, TRICHOMELESS1 (TCL1), which negatively regulates trichome formation on the inflorescence stems and pedicels by directly suppressing the expression of GL1. RESULTS: We analyzed here the role of TRICHOMELESS2 (TCL2), a previously-uncharacterized single-repeat MYB transcription factor in trichome patterning in Arabidopsis. We showed that TCL2 is closely related to TCL1, and like TCL1 and other single-repeat MYBs, TCL2 interacts with GL3. Overexpression of TCL2 conferred glabrous phenotype while knockdown of TCL2 via RNAi induced ectopic trichome formation on the inflorescence stems and pedicels, a phenotype that was previously observed in tcl1 mutants. These results suggested that TCL2 may have overlapping function with TCL1 in controlling trichome formation on inflorescences. On the other hand, although the transcription of TCL2, like TCL1, is not controlled by the activator complex formed by GL1 and GL3, and TCL2 and TCL1 proteins are more than 80% identical at the amino acid level, the expression of TCL2 under the control of TCL1 promoter only partially recovered the mutant phenotype of tcl1, implying that TCL2 and TCL1 are not fully functional equivalent. CONCLUSIONS: TCL2 function redundantly with TCL1 in controlling trichome formation on inflorescences, but they are not fully functional equivalent. Transcription of TCL2 is not controlled by activator complex formed by GL1 and GL3, but MIR156 controlled SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) transcription factors. However, SPLs might require co-activators to regulate the expression of their target genes, including TCL1, TRY and possibly, TCL2.

Dataset Information

A single amino acid replacement in ETC2 shapes trichome patterning in natural Arabidopsis populations.

Publications

A single amino acid replacement in ETC2 shapes trichome patterning in natural Arabidopsis populations.

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