Loss-of-function of MIR172b and prime editing of SNB reveal a regulatory module underlying cleistogamy in rice.
Shim SH, Piao R, Seo DY, Lee SK, Park SY
Crispr
Rice paddies breeding cleistogamous varieties could produce seed that stays genetically pure season after season without cross-pollination — the same principle that keeps heirloom seed lines true, scaled to one of the world's staple crops.
Rice flowers normally open briefly so pollen can spread, but some rice plants stay closed and pollinate themselves — a trait called cleistogamy. Researchers tracked this behavior to a tiny molecular switch: a small RNA that dials down a gene responsible for forming the fleshy pads that push the flower open. When that small RNA is missing, the gene runs at full blast, the pads never develop properly, and the flower stays shut.
Key Findings
A 4.6-kilobase deletion in the natural rice mutant 'ld' eliminates the miR172b gene, causing nearly complete absence of the miR172b small RNA in young flower tissue.
Prime editing of the miR172-binding site in the SNB gene — a single targeted DNA change — was sufficient to reproduce the closed-flower phenotype, confirming SNB as the direct downstream target.
Promoter reporter experiments showed miR172b and SNB are expressed in the same lodicule cells during flower development, placing them in the same regulatory pathway.
chevron_right Technical Summary
Scientists identified the genetic switch that causes rice flowers to stay closed and self-fertilize — a trait called cleistogamy — by discovering that a small RNA molecule (miR172b) keeps a key flower-opening gene (SNB) suppressed. When miR172b is lost, SNB runs unchecked and the flower parts that normally push the flower open fail to develop properly.
Abstract Preview
Cleistogamy, or self-fertilization of a closed flower, can limit unintended gene flow and may contribute to varietal purity in rice (Oryza sativa), with potential value for transgene containment. W...
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