Ultraviolet-B radiation induces cell death in root tips and reprograms metabolism in Arabidopsis

Abstract

Ultraviolet-B (UV-B) radiation inhibits root system growth, however, the influence of UV-B radiation on the regulation of root development remains unclear. Here, we investigated the effects of UV-B radiation on root growth and metabolism in Arabidopsis using physiological, pharmacological, and transcriptome approaches. Our previous study has demonstrated that UV-B radiation depresses auxin accumulation in roots by reducing auxin biosynthesis, transport, and response. In this study, we found that UV-B radiation inhibited primary root (PR) growth by inducing root tip cell death and thereby disrupting cell division and elongation in root tips. The destructed root structure and distorted auxin flow caused by UV-B-induced root tip cell death also led to a reduced auxin accumulation in roots. Supplementation with an auxin α-naphthylacetic acid alleviated UV-B-repressed PR growth and further supported a notion that auxin is involved in UV‑B-repressed PR growth. The UV-B radiation downregulated the expression of genes encoding the enzymes or regulators of the biosyntheses and degradations of the structural constituents of cell wall and genes involved in wax, cutin, and suberin biosyntheses, thereby repressing root system growth and development. The UV-B radiation also markedly repressed photosynthesis-related gene expression in roots, a non-photosynthetic organ. Taken together, this study suggests that UV-B radiation affects root growth by inducing cell death in root tips and reprogramming metabolism in roots.