National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430070, China.
Southern Cross Plant Science, Southern Cross University, Lismore, NSW, 2480, Australia.
New Phytol. 2019 Apr;222(2):837-851. doi: 10.1111/nph.15632. Epub 2019 Jan 5.
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.IAA7). A G-to-A mutation changed the glycine at the 84 position to glutamic acid (G84E), disrupting the conserved degron motif GWPPV and reducing the affinity between BnaA3.IAA7 and TIR1 (TRANSPORT INHIBITOR RESPONSE 1) in an auxin dosage-dependent manner. This change repressed the degradation of BnaA3.IAA7 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.IAA7 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.
植物结构是许多作物整体产量的关键因素。油菜（甘蓝型油菜）是一种重要的全球油料作物，其植物结构的遗传基础尚不清楚。我们对乙基磺酸甲酯（EMS）诱变油菜突变体 sca 进行了特征描述，该突变体具有多种表型改变，包括皱叶、半矮秆、窄分枝角度和向上直立的角果。我们鉴定了该基因，它编码Aux/IAA 蛋白（BnaA3.IAA7）。一个 G 到 A 的突变使第 84 位的甘氨酸突变为谷氨酸（G84E），破坏了保守的降解元件 GWPPV，并以生长素剂量依赖的方式降低了 BnaA3.IAA7 与 TIR1（TRANSPORT INHIBITOR RESPONSE 1）之间的亲和力。这种变化抑制了 BnaA3.IAA7 的降解，因此抑制了低水平生长素的信号转导，从而缩短了节间的长度。G84E 突变通过增强向地性反应来增加分枝角度。杂合体 +/sca 非常类似于理想的植物结构，通过单基因超显性提高多个组成性状，表现出强烈的杂种产量优势。我们的研究结果表明，BnaA3.IAA7 中的弱功能获得性突变通过改善植物结构有助于杂种产量优势，这对于培育优良的油菜杂交品种非常有价值，这种突变可能会提高其他芸苔属作物的产量。
