Chen Weifeng, Xiao Zhengcao, Wang Yule, Wang Jinxiao, Zhai Rui, Lin-Wang Kui, Espley Richard, Ma Fengwang, Li Pengmin
State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, Shaanxi, 712100, China.
College of Food Science and Technology, Northwest University, Xi'an, Shaanxi, 710069, China.
Hortic Res. 2021 Aug 1;8(1):173. doi: 10.1038/s41438-021-00609-9.
Flavonoids play important roles in regulating plant growth and development. In this study, three kaempferol 3-O-glycosides were identified and mainly accumulated in flowers but not in leaves or fruits of Malus. In Malus, flower petal color is normally white, but some genotypes have red flowers containing anthocyanin. Anthocyanin biosynthesis appears to be in competition with kaempferol 3-O-glycosides production and controlled by the biosynthetic genes. The white flower Malus genotypes had better-developed seeds than the red flower genotypes. In flowers, the overexpression of MYB10 in Malus domestica enhanced the accumulation of anthocyanin, but decreased that of kaempferol 3-O-glycosides. After pollination the transgenic plants showed slower pollen tube growth and fewer developed seeds. Exogenous application of different flavonoid compounds suggested that kaempferol 3-O-glycosides, especially kaempferol 3-O-rhamnoside, regulated pollen tube growth and seed set rather than cyanidin or quercetin 3-O-glycosides. It was found that kaempferol 3-O-rhamnoside might regulate pollen tube growth through effects on auxin, the Rho of plants (ROP) GTPases, calcium and the phosphoinositides signaling pathway. With the inhibition of auxin transport, the transcription levels of Heat Shock Proteins (HSPs) and ROP GTPases were downregulated while the levels were not changed or even enhanced when blocking calcium signaling, suggesting that HSPs and ROP GTPases were downstream of auxin signaling, but upstream of calcium signaling. In summary, kaempferol glycoside concentrations in pistils correlated with auxin transport, the transcription of HSPs and ROP GTPases, and calcium signaling in pollen tubes, culminating in changes to pollen tube growth and seed set.
类黄酮在调节植物生长发育中发挥着重要作用。在本研究中，鉴定出三种山奈酚3 - O - 糖苷，它们主要积累在苹果属植物的花中，而不在叶片或果实中。在苹果属植物中，花瓣颜色通常为白色，但一些基因型具有含有花青素的红色花朵。花青素生物合成似乎与山奈酚3 - O - 糖苷的产生存在竞争，并受生物合成基因控制。白花苹果属基因型的种子比红花基因型的发育更好。在花中，苹果中MYB10的过表达增强了花青素的积累，但降低了山奈酚3 - O - 糖苷的积累。授粉后，转基因植物的花粉管生长较慢且发育的种子较少。不同类黄酮化合物的外源施用表明，山奈酚3 - O - 糖苷，尤其是山奈酚3 - O - 鼠李糖苷，调节花粉管生长和结实，而不是花青素或槲皮素3 - O - 糖苷。研究发现，山奈酚3 - O - 鼠李糖苷可能通过影响生长素、植物Rho（ROP）GTP酶、钙和磷酸肌醇信号通路来调节花粉管生长。随着生长素运输的抑制，热休克蛋白（HSPs）和ROP GTP酶的转录水平下调，而当阻断钙信号时，这些水平没有变化甚至升高，这表明HSPs和ROP GTP酶在生长素信号下游，但在钙信号上游。总之，雌蕊中山奈酚糖苷浓度与生长素运输、HSPs和ROP GTP酶的转录以及花粉管中的钙信号相关，最终导致花粉管生长和结实的变化。
