AUTHOR=Zhang Man , Shen Jianshuang , Wu Yutong , Zhang Xiaolu , Zhao Zhengtian , Wang Jia , Cheng Tangren , Zhang Qixiang , Pan Huitang 

TITLE=Comparative transcriptome analysis identified ChlH and POLGAMMA2 in regulating yellow-leaf coloration in Forsythia

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.1009575

DOI=10.3389/fpls.2022.1009575

ISSN=1664-462X

ABSTRACT=<p>Leaf color is one of the most important features for plants used for landscape and ornamental purposes. However, the regulatory mechanism of yellow leaf coloration still remains elusive in many plant species. To understand the complex genetic mechanism of yellow-leaf <italic>Forsythia</italic>, we first compared the pigment content and leaf anatomical structure of yellow-leaf and green-leaf accessions derived from a hybrid population. The physiological and cytological analyses demonstrated that yellow-leaf progenies were chlorophyll deficient with defected chloroplast structure. With comparative transcriptome analysis, we identified a number of candidate genes differentially expressed between yellow-leaf and green-leaf <italic>Forsythia</italic> plants. Among these genes, we further screened out two candidates, <italic>ChlH</italic> (magnesium chelatase Subunit H) and <italic>POLGAMMA2</italic> (POLYMERASE GAMMA 2), with consistent relative-expression pattern between different colored plants. To verify the gene function, we performed virus-induced gene silencing assays and observed yellow-leaf phenotype with total chlorophyll content reduced by approximately 66 and 83% in <italic>ChlH</italic>-silenced and <italic>POLGAMMA2-</italic>silenced plants, respectively. We also observed defected chloroplast structure in both <italic>ChlH</italic>-silenced and <italic>POLGAMMA2-</italic>silenced <italic>Forsythia</italic>. Transient over-expression of <italic>ChlH</italic> and <italic>POLGAMMA2</italic> led to increased chlorophyll content and restored thylakoid architecture in yellow-leaf <italic>Forsythia</italic>. With transcriptome sequencing, we detected a number of genes related to chlorophyll biosynthesis and chloroplast development that were responsive to the silencing of <italic>ChlH</italic> and <italic>POLGAMMA2</italic>. To summarize, <italic>ChlH</italic> and <italic>POLGAMMA2</italic> are two key genes that possibly related to yellow-leaf coloration in <italic>Forsythia</italic> through modulating chlorophyll synthesis and chloroplast ultrastructure. Our study provided insights into the molecular aspects of yellow-leaf <italic>Forsythia</italic> and expanded the knowledge of foliage color regulation in woody ornamental plants.</p>