Biotechnology Bulletin ›› 2026, Vol. 42 ›› Issue (6): 149-163.doi: 10.13560/j.cnki.biotech.bull.1985.2025-0985

Previous Articles    

Molecular Mechanisms and Breeding Applications of Plant Shade Avoidance Response: From Light Signal Perception to Crop Improvement

ZHANG Li1,2,3(), ZHANG Yu1,3, LIU Bin4, NIE Feng-jie1,3, GONG Lei5, HE Ze-xue1,3, LUO Li-jie1, LIU Li-li1, SI Huai-jun2,6()   

  1. 1.Research Center of Agricultural Biotechnology, Ningxia Academy of Agriculture and Forestry Sciences, Yinchuan 750002
    2.College of Agriculture, Gansu Agricultural University, Lanzhou 730070
    3.Ningxia Key Laboratory of Plant Biobreeding, Yinchuan 750002
    4.Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081
    5.Guyuan Branch of Ningxia Academy of Agriculture and Forestry Sciences, Guyuan 756000
    6.State Key Laboratory of Aridl and Crop Science, Gansu Agricultural University, Lanzhou 730070
  • Received:2025-09-13 Online:2026-06-26 Published:2026-07-11
  • Contact: SI Huai-jun E-mail:lesley119@163.com;hjsi@gsau.edu.cn

Abstract:

Shade avoidance syndrome (SAS) encompasses a series of morphological and physiological adaptive responses initiated by plants to cope with competitive shade environments. This is triggered by perceiving light signals such as a decreased red to far-red light ratio (R:FR) and reduced light intensity. SAS significantly impacts the light utilization efficiency of crop populations and their yield potential under high-density planting conditions. Plants perceive changes in environmental light quality primarily through a photoreceptor network centered on phytochromes (PHYs) and cryptochromes (CRYs). Under shade, the reduced activity of these two main photoreceptors cooperatively relieve inhibition on phytochrome-interacting factors (PIFs), leading to large PIF accumulation and the activation of downstream SAS-related gene transcription. As the core hub of signal integration, PIFs positively regulate the synthesis and signal transduction of growth-promoting hormones like auxins and gibberellins, driving cell elongation, while simultaneously suppressing defense signaling, reflecting the adaptive trade-off strategies of plants when competing for light resources. Furthermore, PIFs also mediate the close integration of SAS with signals such as circadian rhythm, carbon and nitrogen metabolism, temperature and salt stress, with its regulatory modules exhibiting both conservation and species-specificity across different crops. This review summarizes advances in SAS molecular mechanisms, systematically elucidating how PHYs and CRYs perceive light quality, and the complex regulatory networks where PIFs act as central hubs integrating hormonal, epigenetic, and circadian clock signals. It specifically compares differences in photosensory system evolution and signal transduction between C3 and C4 crops, and thoroughly discusses molecular breeding strategies, including genome and promoter editing. In addition, the review discusses the balance mechanism between SAS regulation, carbon-nitrogen metabolism, and abiotic stress responses. Future research can leverage single-cell multi-omics technologies to precisely dissect the spatiotemporally specific regulatory networks of SAS signals. This will facilitate the intelligent design of dense planting-tolerant ideotypes, providing robust theoretical guidance and technical support for high-yield crop breeding.

Key words: shade avoidance syndrome, phytochromes, phytochrome-interacting factors, multi-environmental signal integration, molecular breeding