Disturbance of floral colour pattern by activation of an endogenous pararetrovirus, petunia vein clearing virus, in aged petunia plants. (3rd April 2020)

• Record Type: Journal Article
• Authors: Kuriyama, Kazunori; Tabara, Midori; Moriyama, Hiromitsu; Kanazawa, Akira; Koiwa, Hisashi; Takahashi, Hideki; Fukuhara, Toshiyuki
• Is Part Of: Plant journal. Volume 103:Number 2(2020)
• Page Start: 497
• Page End: 511
• Publication Date: 2020-04-03
• Subjects: petunia vein clearing virus -- petunia -- bicolour petal -- post‐transcriptional gene silencing -- DNA methylation -- pararetrovirus -- ageing; Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.14728
• Languages: English
• ISSNs: 0960-7412

Abstract

Summary: White areas of star‐type bicolour petals of petunia ( Petunia hybrida ) are caused by post‐transcriptional gene silencing (PTGS) of the key enzyme of anthocyanin biosynthesis. We observed blotched flowers and a vein‐clearing symptom in aged petunia plants. To determine the cause of blotched flowers, we focused on an endogenous pararetrovirus, petunia vein clearing virus (PVCV), because this virus may have a suppressor of PTGS (VSR). Transcripts and episomal DNAs derived from proviral PVCVs accumulated in aged plants, indicating that PVCV was activated as the host plant aged. Furthermore, DNA methylation of CG and CHG sites in the promoter region of proviral PVCV decreased in aged plants, suggesting that poor maintenance of DNA methylation activates PVCV. In parallel, de novo DNA methylation of CHH sites in its promoter region was also detected. Therefore, both activation and inactivation of PVCV occurred in aged plants. The accumulation of PVCV transcripts and episomal DNAs in blotched regions and the detection of VSR activity support a mechanism in which suppression of PTGS by PVCV causes blotched flowers. Significance Statement: The activation process of an endogenous pararetrovirus, petunia vein clearing virus (PVCV), and the effect of its activation on the bicolour pattern of star‐type petunia were observed. During the long‐term cultivation of petunia plants, the methylation level of the promoter region of PVCV proviruses decreased, an activated PVCV interfered with post‐transcriptional chalcone synthase gene silencing by its suppressor of RNA silencing, and then blotched flowers appeared.