Endogenous overexpression of Poplar MYB186 increases trichome density, improves growth rate and insect pest resistance

Trichomes are specialised epidermal cells that generally play a role in reducing transpiration and act as a deterrent to herbivory. In a screen of activation tagged Populus tremula x P. alba 717-1B4 trees, we identified a mutant line, fuzzy, with increased foliar trichome density. This mutant also had a 35% increase in growth rate and a 200% increase in the rate of photosynthesis as compared to wild-type poplar. The fuzzy mutant had significant resistance to feeding by larvae of the white spotted tussock moth (Orgyia leucostigma), a generalist insect pest of poplar trees. The fuzzy phenotype is attributable to activation tagging and increased expression of the gene encoding PtaMYB186, which is related to Arabidopsis thaliana MYB106, a known regulator of trichome initiation. The fuzzy phenotype can be recapitulated by overexpressing PtaMYB186 in poplar. PtaMYB186 overexpression results in reconfiguration of the poplar transcriptome, with changes in the transcript abundance of suites of genes that are related to trichome differentiation. It is notable that this gene responsible for trichome development also altered traits related to growth rate and pest resistance, suggesting that non-intuitive facets of plant development might be useful targets for plant improvement.

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Plett JM, Wilkins O, Campbell MM, Ralph SG, Regan S