Annals of Botany

miR172 down-regulates the translation of cleistogamy1 in barley

Flower opening in barley (Hordeum vulgare) is induced by the swelling of the lodicule, a trait under the suppressor protein CLY1 encoded by the cleistogamy1 (cly1). Anwar et al. show a small RNA miR172a was the most abundant among three miR172 isomers, and sequence polymorphism at the miR172a target site within cly1 was relevant to the abundance of the CLY1 protein, but not that of its transcript.

Effect of absence of miR172a on inflorescence phenotype and accumulation of CLY1.
Effect of absence of miR172a on inflorescence phenotype and accumulation of CLY1. (A) miR172a/Cly1.a (top) and Ds-miR172a/Cly1.a (bottom) at stages from glume primordium (GP) to maturity (MU). LP, lemma primordium stage; SP, stamen primordium stage; AP, awn primordium stage; WA, white anther stage. (B–D) Variation in lodicule size at anthesis in (B) miR172a/Cly1.a homozygote (C) Ds-miR172a/Cly1.ahomozygote and (D) miR172a/cly1.b homozygote. Scale bars = 1 mm. (E) qRT–PCR-derived transcript abundance of cly1. Actin was the reference transcript. (F) Western blot analysis of CLY1 in miR172a/Cly1.a(WT) and Ds-miR172a/Cly1.a (Ds) (top) and abundance as determined by ratio of CLY1/tubulin abundance (bottom). Values in (E) and (F) are mean and s.e. (n = 3 biological replications). *Means are significantly different at the 5 % probability level; ns, not significantly different.

In a Ds-induced Hv-miR172a null mutant, abundance of the CLY1 protein increased, but not that of its transcript, and the lodicules failed to grow, resulting in a non-opening flower. The implication is that miR172a acts to reduce the translation of cly1, which develops lodicules and enables open-flowering.

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