Molecular Epigenetic Understanding of Seasonal Regulation of Flowering Time in Wheat

doi:10.13560/j.cnki.biotech.bull.1985.2024-0959

Abstract

Abstract:

Wheat（Triticum aestivum, AABBDD）is one of the most important food crops in the world, and is also the second staple food crop in China. The wide adaptability and ecological diversity of wheat varieties is partly determined by their flowering time. Furthermore, flowering time is an important agronomic trait that partly determines the yield and quality of wheat grain. Prolonged cold exposure in winter（winter cold）and increasing daylengths in spring and early summer are two key seasonal factors that ensure winter wheat flowering and bearing fruit at the proper time. The vernalization and photoperiodic pathways have been evolved in winter wheat to integrate the signals of winter cold and daylength changes with developmental state, leading to the floral transition at a proper season for seed production. In this review, we summarize molecular epigenetic progresses on wheat flowering-time regulation, discuss unsolved issues as well as prospects future directions in this field.

Key words: vernalization, photoperiod, regulation of wheat flowering-time, VRN1, PPD1

NIU De, HE Yue-hui. Molecular Epigenetic Understanding of Seasonal Regulation of Flowering Time in Wheat[J]. Biotechnology Bulletin, 2024, 40(10): 30-40.

Figures/Tables 2

Fig. 1 Molecular pathway for photoperiodic regulation of flowering in wheat In long days, phytochromes senses light signals and further inhibits the function of the Evening Complex（EC）, which in turn relieves the repression of PPD1 expression by EC. PPD1 further promotes VRN3 expression, thereby promoting the transition to flowering

Fig. 2 Seasonal factors and flowering regulation of wheat This schematic drawing shows the relationship between the growth cycle of winter wheat and seasons（autumn, September-November; winter, December-February; spring, March-May; summer, June-August）. Winter wheat in China is typically sown in October and November, and harvested in May or June of the coming year. The daylength curve shows the variation trend of daytime in northern regions of China（30°N-50°N）during the seasons. The temperature curve shows the average temperature variation trend in the main winter-wheat production areas in China from 1960 to 2016[103]. After wheat germination, VRN2 expression was activated by light and regulated by circadian clock, VRN2 inhibited VRN3 expression. With the decrease of temperature in winter, the expression of VRN1 was gradually induced and the expression of VRN2 was gradually inhibited. With the increase of daylength and temperature in spring, VRN3 expression was gradually induced by various factors. VRN1-VRN3 constitutes a positive feedback regulation loop, which represses VRN2 expression and promotes the switch from the vegetative phase to reproduction gradually. After the fertilization following flowering, the expression of VRN1 in embryogenesis was turned off in order to start a new life cycle of winter wheat

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