Temporal expression of defence and susceptibility genes and tospovirus accumulation in capsicum chlorosis virus-infected capsicum

Fernanda Yuri Borges Naito,Neena Mitter,Shirani Manel Kumari Widana Gamage,Ralf Georg Dietzgen

doi:10.1007/s00705-022-05401-1

Fernanda Yuri Borges Naito, Neena Mitter + Show 2 more

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https://doi.org/10.1007/s00705-022-05401-1

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Abstract

Yolo Wonder (YW) and Warlock (W), two capsicum cultivars that are susceptible to capsicum chlorosis virus (CaCV), were compared in terms of symptom development, tospovirus accumulation, and host gene expression during the first 12 days post infection (dpi). Temporal expression of selected early CaCV-response genes was used to gain insights into plant-virus interactions and to identify potential targets for CaCV control. Symptoms developed faster in YW during the first seven days of infection, while systemic symptoms were similar in both cultivars at 10 and 12 dpi. CaCV accumulation was higher in YW at 7 dpi despite a lower titre at 3 dpi. At 12 dpi, virus accumulation was similar for both cultivars. Symptom development appears to be correlated to virus accumulation over time for both cultivars. Chalcone synthase (CHS), cytochrome P450 (CYP), and tetraspanin 8-like (TSP8) genes followed a similar expression pattern over time in both cultivars. The thionin gene showed increased expression in CaCV-infected plants at 12 dpi. The WRKY40 gene showed significant differential expression at all time points in YW, but only at 12 dpi in W. The strongest correlation of temporal gene expression and virus titre was seen for CYP, TSP8, thionin, and WRKY40. CHS and CYP may be involved in symptom development, and TSP8 may be involved in virus movement. CHS, CYP, and TSP8 may be good targets for future overexpression or silencing studies to clarify their functions during virus infection and, potentially, for control of CaCV in capsicum.

Highlights

Capsicum chlorosis virus (CaCV) is taxonomically classified as a member of the species Capsicum chlorosis orthotospovirus, genus Orthotospovirus, family Tospoviridae, order Bunyavirales [1]
CaCV symptoms were evaluated at 3, 5, 7, 10, and 12 dpi using a scoring system we developed for capsicum cultivars (Table 2, Fig. 1)
Our observations suggest that cell-to-cell and systemic movement of CaCV is slower in Warlock than in Yolo Wonder early in infection, while virus replication and movement appear to be faster after 7 dpi, leading to similar virus titres in both cultivars at 12 dpi, when symptoms are evident

Summary

Introduction

Capsicum chlorosis virus (CaCV) is taxonomically classified as a member of the species Capsicum chlorosis orthotospovirus, genus Orthotospovirus, family Tospoviridae, order Bunyavirales [1]. CaCV was first reported in 1999 infecting tomato and capsicum crops in Queensland, Australia [2]. Its S segment is composed of 3944 nt and encodes the nucleocapsid (N) protein and a non-structural RNA silencing suppressor (NSs), its M segment of 4846 nt encodes a glycoprotein precursor (Gn/Gc) and a non-structural movement protein (NSm), and its L segment of 8913 nt encodes an RNA-dependent RNA polymerase (L protein) [17]. This isolate has an unusually large intergenic region (1663 nt) in the S segment [17]

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