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Article|01 Aug 2021|OPEN
Competition between anthocyanin and kaempferol glycosides biosynthesis affects pollen tube growth and seed set of Malus
Weifeng Chen1, Zhengcao Xiao1,2, Yule Wang1, Jinxiao Wang1, Rui Zhai1, Kui Lin-Wang3, Richard Espley3, Fengwang Ma1 & Pengmin Li1,
1State 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
2College of Food Science and Technology, Northwest University, Xi’an, Shaanxi 710069, China
3The New Zealand Institute for Plant and Food Research Ltd, Private Bag, 92169 Auckland, New Zealand

Horticulture Research 8,
Article number: 173 (2021)
doi: 10.1038/hortres.2021.173
Views: 141

Received: 06 Dec 2020
Revised: 20 May 2021
Accepted: 01 Aug 2021
Published online: 01 Aug 2021

Abstract

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.