Ultraviolet (UV) radiation is classified according to wavelength as UV-A radiation, UV-B radiation, and UV-C radiation. Among these types, UV-B radiation is of prime importance because it has severely damaging effects on plant growth and development despite its small proportion. UV-B radiation induces positive root phototropic bending; however, the underlying physiological and molecular mechanisms remain unclear.

Prof. XU Jin and his team of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study to investigate the physiological and molecular responses of Arabidopsis roots to UV-B radiation. They investigated whether and how auxin and flavonoids are involved in UV-B radiation-induced root bending in Arabidopsis using physiological, pharmacological, and genetic approaches.

They found that UV-B radiation reduced auxin levels and led to an asymmetric distribution of auxin in root tips, which induced root bending. UV-B radiation modulated the direction of root growth by decreasing IAA biosynthesis and affecting auxin distribution in the root tips, where reduced auxin accumulation and asymmetric auxin distribution were observed. UV-B radiation increased the distribution of auxin on the nonradiated side of the root tips, promoting growth and causing root bending.

Further study indicated the involvement of flavonoids in the IAA-mediated root bending response to UV-B radiation.  UVR8-dependent flavonoid production and its asymmetric accumulation in root tips are associated with UV-B-mediated root phototropic bending through decreased auxin accumulation and induction of asymmetric auxin distribution in root tips by modulating the distribution of AUX1 and PIN2.

The results indicate that UV-B radiation-induced root bending occurred through a flavonoid-mediated phototropic response to UV-B radiation.

The study entitled “UV-B Radiation Induces Root Bending Through the Flavonoid-Mediated Auxin Pathway in Arabidopsis” has been published in Frontiers in Plant Science.

Contact

XU Jin, Ph.D Principal Investigator
Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, Yunnan, China
E-mail:  xujin@xtbg.ac.cn
Tel: +86 871 65140420