Wu Xiaomei, Tian Yuxiao, Li Weihuan, An Jiaqing, Wu Zhijian, Huang Lu, Wang Junwei, Hu Zhenzhu, Huang Ke, Wu Qiuyun
College of Horticulture, Hunan Agricultural University, Changsha, 410128, Hunan, China.
Engineering Research Center for Horticultural Crop Germplasm Creation and New Variety Breeding, Ministry of Education, Changsha, 410128, Hunan, China.
Theor Appl Genet. 2025 Sep 1;138(9):236. doi: 10.1007/s00122-025-05027-2.
Broccoli is an economically significant vegetable with high nutritional and medicinal value. Seed size/weight is one of the important agronomic traits that determine crop yield, which is regulated by multiple plant hormones. However, limited information is known about the regulation of seed size control in broccoli. Here, we report that the basic helix-loop-helix transcription factor BoMYC2 exerts a negative regulatory influence on seed-related traits in broccoli. The overexpression of BoMYC2 in Arabidopsis and broccoli led to notably decreased seed size and seed weight, likely by repressing cell proliferation of embryonic. Besides, overexpression of BoMYC2 increased the fatty acid accumulation while reducing the protein and soluble sugar levels in stably transgenic broccoli seeds, affecting seed storage compounds composition and seed size. Based on DNA affinity purification sequencing, BoMYC2 targeted the cytokinin oxidase gene BoCKX5 by binding to the G-box motif in its promoter regions. BoMYC2 activated the expression of BoCKX5 to modulate cytokinin metabolism. The expression levels of cytokinin-related genes and jasmonic acid-related genes were further analyzed in transgenic broccoli seeds, implying that BoMYC2 leads to higher jasmonic acid and lower cytokinin hormone content, which might affect the cell proliferation in seeds. Furthermore, cytokinin levels were significantly lower in BoMYC2-overexpressing broccoli than in wild-type plants. Collectively, these findings reveal a BoMYC2-BoCKX5 regulatory module that controls seed size/weight, enriching our understanding of the internal mechanism in seed size regulation and providing promising targets for high-yield broccoli breeding.
西兰花是一种具有重要经济意义的蔬菜，具有很高的营养和药用价值。种子大小/重量是决定作物产量的重要农艺性状之一，它受多种植物激素的调控。然而，关于西兰花种子大小控制的调控机制，我们所知的信息有限。在此，我们报道了碱性螺旋-环-螺旋转录因子BoMYC2对西兰花种子相关性状发挥负调控作用。在拟南芥和西兰花中过表达BoMYC2导致种子大小和重量显著降低，可能是通过抑制胚胎细胞增殖实现的。此外，BoMYC2过表达增加了稳定转基因西兰花种子中的脂肪酸积累，同时降低了蛋白质和可溶性糖水平，影响种子储存化合物的组成和种子大小。基于DNA亲和纯化测序，BoMYC2通过结合其启动子区域的G-box基序靶向细胞分裂素氧化酶基因BoCKX5。BoMYC2激活BoCKX5的表达以调节细胞分裂素代谢。在转基因西兰花种子中进一步分析了细胞分裂素相关基因和茉莉酸相关基因的表达水平，这表明BoMYC2导致较高的茉莉酸和较低的细胞分裂素激素含量，这可能影响种子中的细胞增殖。此外，过表达BoMYC2的西兰花中的细胞分裂素水平显著低于野生型植株。总的来说，这些发现揭示了一个控制种子大小/重量的BoMYC2-BoCKX5调控模块，丰富了我们对种子大小调控内在机制的理解，并为高产西兰花育种提供了有前景的靶点。
