Transcriptome analysis of Iris japonica var. variegata for chlorophyll and photosynthesis-related pathways involved in white–green striped leaves

Abstract

As a well-known garden plant, many beautiful iris flower phenotypes and leaf variegation have been created. Iris japonica var. variegata is a variant of I. japonica that has a white–green striped leaf color genotype. It has high horticultural value, but its underlying molecular mechanisms remain unclear. Here, we analyzed the physiological features and ultrastructural observation of white and green tissues. In our study, the results showed that the phenotype was related to the abnormal chloroplast morphology and deficiencies in chlorophyll. To understand the mechanisms for these observations, we used Illumina sequencing technology to identify the transcriptome and profile differentially expressed genes (DEGs). We identified 1327 DEGs in white leaf tissues compared with green leaf tissues, including 342 upregulated genes and 985 downregulated DEGs. The downregulated DEGs included porphyrin and chlorophyll metabolism, chloroplast development, and photosynthetic pathways. Changes in the expression of genes (CYSG and GLK) involved in these pathways could be responsible for the phenotype of I. japonica var. variegata. To our knowledge, this is the first time that evidence has been provided to better understand the primary cause of chloroplast structure in white–green striped leaves for iris and will be valuable for the iris breeding industry.