LAUSR

Melatonin functions as a plant growth regulator in a concentration-dependent manner. In this study, we investigated the effects of melatonin on root growth and dissected underlined mechanisms. The results showed that melatonin up to 1000 μM inhibited primary root growth, but promoted lateral root development. Through RNA sequencing analysis, functions of differentially expressed genes were mainly involved in stress response, signaling transduction, transport, hormone metabolism and amino acid metabolism. Genes involving in jasmonate (JA), brassinosteroid (BR) and cytokinin (CK) biosynthesis were inhibited, but these in ethylene (ET), strigolactone (SL) and gibberellins (GA) biosynthetic pathways were activated after melatonin treatment. The majority of zinc finger proteins (ZFPs), Calmodulin-like (CMLs), NAM, ATAF1/2, and CUC2 (NACs) and ubiquitination related genes (RING/U-box and F-box) were upregulated, which possibly acted downstream of integrated hormone signals to mediate root growth. This study characterized melatonin modulated networks in regulating root growth.