AUTHOR=Jeong Hyo-Bong , Jang So-Jeong , Kang Min-Young , Kim Suna , Kwon Jin-Kyung , Kang Byoung-Cheorl 

TITLE=Candidate Gene Analysis Reveals That the Fruit Color Locus C1 Corresponds to PRR2 in Pepper (Capsicum frutescens)

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.00399

DOI=10.3389/fpls.2020.00399

ISSN=1664-462X

ABSTRACT=<p>The diverse fruit colors of peppers (<italic>Capsicum</italic> spp.) are due to variations in carotenoid composition and content. Mature fruit color in peppers is regulated by three independent loci, <italic>C1</italic>, <italic>C2</italic>, and <italic>Y</italic>. <italic>C2</italic> and <italic>Y</italic> encode phytoene synthase (PSY1) and capsanthin-capsorubin synthase (CCS), respectively; however, the identity of the <italic>C1</italic> gene has been unknown. With the aim of identifying <italic>C1</italic>, we analyzed two pepper accessions with different fruit colors: <italic>Capsicum frutescens</italic> AC08-045 and AC08-201, whose fruits are light yellow and white, respectively. Ultra-performance liquid chromatography showed that the total carotenoid content was six times higher in AC08-045 than in AC08-201 fruits, with similar composition of main carotenoids and slight difference in minor components. These results suggest that a genetic factor in AC08-201 may down-regulate overall carotenoid biosynthesis. Analyses of candidate genes related to carotenoid biosynthesis and plastid abundance revealed that both accessions carry non-functional alleles of <italic>CCS</italic>, <italic>golden2-like transcription factor</italic> (<italic>GLK2</italic>), and <italic>PSY1.</italic> However, a nonsense mutation (C2571T) in <italic>PRR2</italic>, a homolog of <italic>Arabidopsis pseudo response regulator2-like</italic> (<italic>APRR2</italic>), was present in only AC08-201. In a population derived from a cross between AC08-045 and AC08-201, a SNP marker based on the nonsense mutation co-segregated fully with fruit color, implying that the mutation in <italic>PRR2</italic> may cause the white color of AC08-201 fruits. Transmission electron microscopy (TEM) of AC08-201 fruit pericarp also showed less developed granum structure in chloroplast and smaller plastoglobule in chromoplast compared to those of AC08-045. Virus-induced gene silencing (VIGS) of <italic>PRR2</italic> significantly reduced carotenoid accumulation in <italic>Capsicum annuum</italic> ‘Micropep Yellow’, which carries non-functional mutations in both <italic>PSY1</italic> and <italic>CCS</italic>. Furthermore, sequence analysis of <italic>PSY1</italic>, <italic>CCS</italic>, and <italic>PRR2</italic> in other white pepper accessions of <italic>C. annuum</italic> and <italic>Capsicum chinense</italic> showed that they commonly have non-functional alleles in <italic>PSY1</italic>, <italic>CCS</italic>, and <italic>PRR2</italic>. Thus, our data demonstrate that the fruit color locus <italic>C1</italic> in <italic>Capsicum</italic> spp. corresponds to the gene <italic>PRR2</italic>.</p>