Increasing grain yield has always been the primary goal of crop breeding. KLUH/CYP78A5 has been shown to affect seed size in several plant species, but the relevant molecular mechanism is still unclear and there are no reports of this gene contributing to yield. Here, we demonstrate that modified expression of TaCYP78A5 can enhance wheat grain weight and grain yield per plant by accumulating auxin. TaCYP78A5 is highly expressed in maternal tissues, including ovary and seed coat during wheat development. The constitutive overexpression of TaCYP78A5 leads to significantly increased seed size and weight but not grain yield per plant due to the strengthening of apical dominance. However, localized overexpression of TaCYP78A5 in maternal integument enhances grain weight and grain yield per plant by 4.3%–18.8% and 9.6%–14.7%, respectively, in field trials. Transcriptome and hormone metabolome analyses reveal that TaCYP78A5 participates in auxin synthesis pathway and promotes auxin accumulation and cell wall remodelling in ovary. Phenotype investigation and cytological observation show that localized overexpression of TaCYP78A5 in ovary results in delayed flowering and prolonged proliferation of maternal integument cells, which promote grain enlargement. Moreover, naturally occurring variations in the promoter of TaCYP78A5-2A contribute to thousand-grain weight (TGW) and grain yield per plant of wheat;TaCYP78A5-2A haplotype Ap-HapII with higher activity is favourable for improving grain weight and grain yield per plant and has been positively selected in wheat breeding. Then, a functional marker of TaCYP78A5 haplotype Ap-HapII is developed for marker-assisted selection in wheat grain and yield improvement.

中文翻译：

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TaCYP78A5 的修饰表达通过在小麦 (Triticum aestivum L.) 中积累生长素来提高粒重和产量潜力

提高粮食产量一直是作物育种的首要目标。KLUH/CYP78A5已被证明会影响几种植物的种子大小，但相关的分子机制仍不清楚，也没有关于该基因有助于产量的报道。在这里，我们证明了TaCYP78A5的修饰表达可以通过积累生长素来提高小麦粒重和单株籽粒产量。TaCYP78A5在小麦发育过程中在母体组织（包括子房和种皮）中高度表达。由于顶端优势的加强， TaCYP78A5的组成型过表达导致种子大小和重量显着增加，但不是每株植物的籽粒产量。然而，TaCYP78A5的局部过表达在田间试验中，母体珠被中的粒重和单株产量分别提高了 4.3%–18.8% 和 9.6%–14.7%。转录组和激素代谢组分析表明，TaCYP78A5参与生长素合成途径，促进卵巢中生长素积累和细胞壁重塑。表型研究和细胞学观察表明，TaCYP78A5在卵巢中的局部过表达导致母体珠被细胞开花延迟和增殖延长，从而促进籽粒增大。此外， TaCYP78A5-2A启动子的天然变异有助于小麦的千粒重 (TGW) 和单株产量；TaCYP78A5-2A单倍型Ap-Hap活性较高的Ⅱ有利于提高粒重和单株产量，已在小麦育种中被积极选择。然后，开发了TaCYP78A5单倍型Ap-Hap II的功能标记，用于小麦籽粒的标记辅助选择和产量提高。