Metabolic Reprogramming in Leaf Lettuce Grown Under Different Light Quality and Intensity Conditions Using Narrow-Band LEDs

Kazuyoshi Kitazaki,Richard W Michelmore,Miyako Kusano,Atsushi Fukushima,Yozo Okazaki,Tomoko Nishizawa,Tetsuya Mori,Kazuki Saito,Makoto Kobayashi,Ryo Nakabayashi,Kazuhiro Shoji,Sebastian Reyes-Chin-Wo

doi:10.1038/s41598-018-25686-0

Abstract

Light-emitting diodes (LEDs) are an artificial light source used in closed-type plant factories and provide a promising solution for a year-round supply of green leafy vegetables, such as lettuce (Lactuca sativa L.). Obtaining high-quality seedlings using controlled irradiation from LEDs is critical, as the seedling health affects the growth and yield of leaf lettuce after transplantation. Because key molecular pathways underlying plant responses to a specific light quality and intensity remain poorly characterised, we used a multi-omics–based approach to evaluate the metabolic and transcriptional reprogramming of leaf lettuce seedlings grown under narrow-band LED lighting. Four types of monochromatic LEDs (one blue, two green and one red) and white fluorescent light (control) were used at low and high intensities (100 and 300 μmol·m−2·s−1, respectively). Multi-platform mass spectrometry-based metabolomics and RNA-Seq were used to determine changes in the metabolome and transcriptome of lettuce plants in response to different light qualities and intensities. Metabolic pathway analysis revealed distinct regulatory mechanisms involved in flavonoid and phenylpropanoid biosynthetic pathways under blue and green wavelengths. Taken together, these data suggest that the energy transmitted by green light is effective in creating a balance between biomass production and the production of secondary metabolites involved in plant defence.

Highlights

Response[14,15]
Our multivariate statistical analyses showed that samples clustered in different areas of the scatter plot, with each cluster representing plants exposed to red Light-emitting diodes (LEDs), blue LEDs and white fluorescent light (Figs S1a and b)
To validate RNA-Seq data, we examined six flavonoid biosynthesis genes that were significantly down-regulated by green and red LEDs, i.e. phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), flavonoid 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS) and UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT) using quantitative reverse transcription PCR (Fig. 5). qRT-PCR analysis confirmed that the expression of these genes was reduced after exposure to green and red LEDs to levels lower than those achieved after fluorescent light (FL) exposure (Fig. S11)

Summary

Introduction

Response[14,15]. Plants are usually highly sensitive to the type and intensity of light during initial growth stages[15]. To determine the effect of light quality on plant growth, studies have been conducted using blue light, red light and a combination of the two[11,16,17,18,19]. Global metabolic and transcriptional responses to monochromatic light delivered by LEDs of different colours remain under-characterised and poorly understood. It is unclear whether small changes in the light spectrum of green light elicit detectable effects in plant growth and development. We used systems biology approach to evaluate the impact of variable light quality and intensity using narrow-band LED lighting on metabolic and transcriptional reprogramming in leaf lettuce. Data obtained in this study highlight key potential metabolic pathways and morphological variations in leaf lettuce

Objectives

Methods

Results

Conclusion