An auxin signaling gene BnaA3.IAA7 contributes to improved plant architecture and yield heterosis in rapeseed

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Abstract

Summary Plant architecture is the key factor affecting overall yield in many crops. The genetic basis underlying plant architecture in rapeseed ( Brassica napus ), a key global oil crop, is elusive. We characterized an ethyl methanesulfonate ( EMS) ‐mutagenized rapeseed mutant, sca , which had multiple phenotypic alterations, including crinkled leaves, semi‐dwarf stature, narrow branch angles and upward‐standing siliques. We identified the underlying gene, which encodes an Aux/ IAA protein (BnaA3. IAA 7). A G‐to‐A mutation changed the glycine at the 84 th position to glutamic acid (G84E), disrupting the conserved degron motif GWPPV and reducing the affinity between BnaA3. IAA 7 and TIR 1 ( TRANSPORT INHIBITOR RESPONSE 1) in an auxin dosage‐dependent manner. This change repressed the degradation of BnaA3. IAA 7 and therefore repressed auxin signaling at low levels of auxin that reduced the length of internodes. The G84E mutation reduced branch angles by enhancing the gravitropic response. The heterozygote +/ sca closely resembled a proposed ideal plant architecture, displaying strong yield heterosis through single‐locus overdominance by improving multiple component traits. Our findings demonstrate that a weak gain‐of‐function mutation in BnaA3 . IAA 7 contributes to yield heterosis by improving plant architecture and would be valuable for breeding superior rapeseed hybrid cultivars and such a mutation may increase the yield in other Brassica crops.

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