Plant transcription factors (TFs), such as basic helix-loop-helix (bHLH) and AT-rich zinc-binding proteins (PLATZ), play critical roles in regulating the expression of developmental genes in cereals. We identified the bHLH protein TaPGS1 (T. aestivum Positive Regulator of Grain Size 1) specifically expressed in the seeds at 5–20 days post-anthesis in wheat. TaPGS1 was ectopically overexpressed (OE) in wheat and rice, leading to increased grain weight (up to 13.81% in wheat and 18.55% in rice lines) and grain size. Carbohydrate and total protein levels also increased. Scanning electron microscopy results indicated that the starch granules in the endosperm of TaPGS1 OE wheat and rice lines were smaller and tightly embedded in a proteinaceous matrix. Furthermore, TaPGS1 was bound directly to the E-box motif at the promoter of the PLATZ TF genes TaFl3 and OsFl3 and positively regulated their expression in wheat and rice. In rice, the OsFl3 CRISPR/Cas9 knockout lines showed reduced average thousand-grain weight, grain width, and grain length in rice. Our results reveal that TaPGS1 functions as a valuable trait-associated gene for improving cereal grain yield.

中文翻译：

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PGS1 碱性螺旋-环-螺旋蛋白调节 Fl3 以影响谷物的种子生长和谷物产量

植物转录因子 (TF)，如碱性螺旋-环-螺旋 (bHLH) 和富含 AT 的锌结合蛋白 (PLATZ)，在调节谷物中发育基因的表达中起关键作用。我们鉴定了小麦开花后 5-20 天在种子中特异性表达的 bHLH 蛋白 TaPGS1（T. aestivum Positive Regulator of Grain Size 1）。TaPGS1在小麦和水稻中异位过表达 (OE)，导致籽粒重量增加（小麦高达 13.81%，水稻高达 18.55%）和籽粒大小。碳水化合物和总蛋白水平也增加了。扫描电镜结果表明，TaPGS1胚乳中的淀粉颗粒OE 小麦和水稻品系更小且紧密嵌入蛋白质基质中。此外，TaPGS1 直接与 PLATZ TF 基因TaFl3和OsFl3启动子的 E-box 基序结合，并正向调节它们在小麦和水稻中的表达。在水稻中，OsFl3 CRISPR/Cas9 敲除品系显示水稻平均千粒重、粒宽和粒长降低。我们的研究结果表明，TaPGS1是一种有价值的性状相关基因，可用于提高谷物产量。