ITRAQ-Based Quantitative Proteomics Analysis Reveals the Mechanism of Golden-Yellow Leaf Mutant in Hybrid Paper Mulberry

Fenfen Wang,Naizhi Chen,Shihua Shen

doi:10.3390/ijms23010127

Abstract

Plant growth and development relies on the conversion of light energy into chemical energy, which takes place in the leaves. Chlorophyll mutant variations are important for studying certain physiological processes, including chlorophyll metabolism, chloroplast biogenesis, and photosynthesis. To uncover the mechanisms of the golden-yellow phenotype of the hybrid paper mulberry plant, this study used physiological, cytological, and iTRAQ-based proteomic analyses to compare the green and golden-yellow leaves of hybrid paper mulberry. Physiological results showed that the mutants of hybrid paper mulberry showed golden-yellow leaves, reduced chlorophyll, and carotenoid content, and increased flavonoid content compared with wild-type plants. Cytological observations revealed defective chloroplasts in the mesophyll cells of the mutants. Results demonstrated that 4766 proteins were identified from the hybrid paper mulberry leaves, of which 168 proteins displayed differential accumulations between the green and mutant leaves. The differentially accumulated proteins were primarily involved in chlorophyll synthesis, carotenoid metabolism, and photosynthesis. In addition, differentially accumulated proteins are associated with ribosome pathways and could enable plants to adapt to environmental conditions by regulating the proteome to reduce the impact of chlorophyll reduction on growth and survival. Altogether, this study provides a better understanding of the formation mechanism of the golden-yellow leaf phenotype by combining proteomic approaches.

Highlights

Photosynthesis is one of the most important biological processes and harnesses solar energy to provide biochemical energy and oxygen for humans
We investigated the effects of the proteome by isobaric tags for relative and absolute quantitation (iTRAQ) technology combined with liquid chromatography and tandem mass spectrometry (LC-MS/MS) and identified the differentially accumulated proteins related to pigment biosynthesis and metabolism
The mutant was a spontaneous mutant with a golden-yellow leaf phenotype and was smaller than the green leaf plant throughout the developmental stage (Figure 1A)

Summary

Introduction

Photosynthesis is one of the most important biological processes and harnesses solar energy to provide biochemical energy and oxygen for humans. Chloroplasts are heavily involved in both the harvesting of light and the transduction of energy, making them important organelles in the photosynthetic cells of higher plants by supplying both carbon and energy. The thylakoid membrane is in the space where PSI and PSII work and is responsible for harnessing light energy. Chlorophyll is distributed in chloroplast thylakoid membranes, is a major component of the light-harvesting complex, and plays an indispensable role in photosynthesis [5,6]. Leaf color mutants are widely used to identify regulatory mechanisms for chlorophyll biosynthesis, chloroplast development, and photosynthesis. Many reports have shown that most leaf color mutations are related to changes in chloroplast structure and function [8], chlorophyll biosynthesis and degradation mechanisms [9], and photosynthesis [10,11]. In rice, mutations in the genes that encode glutamyl-tRNA [12], mg-chelatase [13], and magnesium-protoporphyrin IX monomethyl ester cyclase [14] lead to changes in leaf color

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Results

Discussion

Conclusion