Prof. Bing-Kai Hou's group at School of Life Sciences, Shandong University made new progress in the research of plant hormone glycosylation. This study have been published in the international top journal PNAS, entitled "IPyA glucosylation mediates light and temperature signaling to regulate auxin-dependent hypocotyl elongation in Arabidopsis" (PNAS, 2020, 117: 6910-6917). This article is a PNAS Direct Submission. The first author is Ph.D. candidate Lu Chen from the School of Life Sciences, and Prof. Hou is the corresponding author.
Auxin is a class of plant hormone that plays a crucial role in the life cycle of plants, particularly in the growth response of plants to ever-changing environments. Since the auxin responses are concentration-dependent and higher auxin concentrations might often be inhibitory, the optimal endogenous auxin level must be closely controlled. However, the underlying mechanism governing auxin homeostasis remains largely unknown. In this study, a UDP-glycosyltransferase (UGT76F1) was identified from Arabidopsis thaliana, which participates in the regulation of auxin homeostasis by glucosylation of indole-3-pyruvic acid (IPyA), a major precursor of the auxin indole-3-acetic acid (IAA) biosynthesis, in the formation of IPyA glucose conjugates (IPyA-Glc). In addition, UGT76F1 was found to mediate hypocotyl growth by modulating active auxin levels in a light- and temperature-dependent manner. Moreover, the transcription of UGT76F1 was demonstrated to be directly and negatively regulated by PIF4, which is a key integrator of both light and temperature signaling pathways. This study sheds a new light on the trade-off between IAA biosynthesis and IPyA-Glc formation in controlling auxin levels, demonstrating that IPyA-Glc formation is a key "watershed" event that controls auxin biosynthesis. This study is an important breakthrough in the field of plant hormones and reveals a key regulatory mechanism for plant growth adaptation to environmental changes through the glucosylation of auxin precursor IPyA.
Prof. Hou’s group has long been engaged in the study of biological function and regulation mechanism of plant molecular glycosylation. In recent years, this group has made a series of progress in this field and published papers with significant influence in New Phytol (2012), The Plant J (2016), The Plant J (2017), Plant Physiol (2018), and Plant Physiol (2019). This publication in PNAS is another important advance made by Hou’s group in the field of plant molecular glycosylation. Prof. Lang-tao Xiao and Dr. Jian-hua Tong from Hunan Agricultural University and Prof. Zhao-Jun Ding from Shandong University contributed to this work. After its publication, this work got the special introduction and commentary entitled “Sugar rush: Glucosylation of IPyA attenuates auxin levels”(PNAS, 2020, 117: 7558-7560) by Professor Lucia C. Strader and Arielle L. Homayouni from Washington University, USA.