Cytological and Transcriptomic Analysis Provide Insights into the Formation of Variegated Leaves in Ilex × altaclerensis 'Belgica Aurea'.

Qiang Zhang,Mingzhuo Hao,Min Zhang,Peng Zhou,Jing Huang

doi:10.3390/plants10030552

Abstract

Ilex × altaclerensis ‘Belgica Aurea’ is an attractive ornamental plant bearing yellow-green variegated leaves. However, the mechanisms underlying the formation of leaf variegation in this species are still unclear. Here, the juvenile yellow leaves and mature variegated leaves of I. altaclerensis ‘Belgica Aurea’ were compared in terms of leaf structure, pigment content and transcriptomics. The results showed that no obvious differences in histology were noticed between yellow and variegated leaves, however, ruptured thylakoid membranes and altered ultrastructure of chloroplasts were found in yellow leaves (yellow) and yellow sectors of the variegated leaves (variegation). Moreover, the yellow leaves and the yellow sectors of variegated leaves had significantly lower chlorophyll compared to green sectors of the variegated leaves (green). In addition, transcriptomic sequencing identified 1675 differentially expressed genes (DEGs) among the three pairwise comparisons (yellow vs. green, variegation vs. green, yellow vs. variegation). Expression of magnesium-protoporphyrin IX monomethyl ester (MgPME) [oxidative] cyclase, monogalactosyldiacylglycerol (MGDG) synthase and digalactosyldiacylglycerol (DGDG) synthase were decreased in the yellow leaves. Altogether, chlorophyll deficiency might be the main factors driving the formation of leaf variegation in I. altaclerensis ‘Belgica Aurea’.

Highlights

Variegated leaves are the leaves with regular or irregular non-green spots and patches on the leaf surface [1]
The palisade tissue and spongy tissue were obviously differentiated in the yellow leaves (y), whereas, few chloroplasts were found in mesophyll tissue (Figure 1B)
Leaf variegation is a phenotype frequently observed in higher plants, which occurs naturally or by mutagenesis [19]

Summary

Introduction

Variegated leaves are the leaves with regular or irregular non-green spots and patches on the leaf surface [1]. This special attractive trait increases the economic value of ornamental plants, and the variegated leaf plants have been widely used in urban landscaping. The defensive mechanisms of foliar variegation were not fully understood. It was proposed that apart from protective role, leaf variegation had some potential physiological advantages. The work of Shelef et al showed that white variegation of Silybum marianum could elevate leaf temperature during cold winter days [4]. Further study revealed that low temperature protective function of leaf variegation was partly associated with increased

Methods

Results

Conclusion