Lowering intercellular melatonin levels by transgenic analysis of indoleamine 2,3-dioxygenase from rice in tomato plants

Abstract

Melatonin exists in numerous living organisms including vertebrates, insects, fungi, bacteria, and plants. Extensive studies have been conducted on the physiological roles of melatonin in various plant species. In plants, melatonin seems to act in antioxidant protection, as a growth promoter, and in photoperiodism. However, the mechanisms by which melatonin carries out these roles remain unclear. We manipulated the endogenous melatonin content in tomato plants by modifying the metabolic enzyme indoleamine 2,3-dioxygenase (IDO). The OsIDO gene was isolated from rice (Oryza sativa) and characterized using 3-D homology modeling and reverse genetic approaches. The amino acid sequence of OsIDO showed high homology to the Ustilago maydis IDO. The 3-D model structure of OsIDO is composed of a small and a large domain. Transgenic tomato plants constitutively expressing the OsIDO gene exhibited a decrease in their melatonin content. Moreover, the number of lateral leaflets decreased in transgenic plants. Protein extracts taken from these plants showed activity degradation, demonstrating the function of OsIDO. These results suggest the involvement of IDO in plant melatonin metabolism and a possible role in plant leaf development.

A new balancing act: The many roles of melatonin and serotonin in plant growth and development

“…Additionally, an effect of MEL on leaf and branching structures has been reported in both rice and tomato 103,104 . A general increase in total biomass due to MEL treatment has been reported, though this may just be a side effect of an increased production of roots, shoots or leaves 91,93,105 .…”

Melatonin as an Endogenous Plant Regulatory Signal: Debates and Perspectives

“…Genetic manipulation of 2,3-dioxygenase revealed a new insight into the role of melatonin in plant development (Okazaki et al 2010). When the gene of 2,3-oxyganase isolated from rice was overexpressed in tomato, the melatonin level decreased, showing reduced numbers of lateral leaflets.…”

Melatonin Regulates Root Meristem by Repressing Auxin Synthesis and Polar Auxin Transport in Arabidopsis

“…Numerous studies have shown that melatonin is widely involved in regulating both the biotic and abiotic stress tolerance, biological rhythms, plant growth and development (seed germination, root architecture, shoot development, plant flowering, fruit ripening, and yield; Kang et al, 2010; Okazaki et al, 2010; Wang et al, 2012; Byeon et al, 2013, 2014b; Yin et al, 2013; Zhang et al, 2013, 2014; Zhao et al, 2013; Byeon and Back, 2014a; Shi and Chan, 2014; Weeda et al, 2014; Shi et al, 2015a,b,c,d,e, 2016). …”