Analysis of external factors that affect formation and accumulation of D-RNAs in Bromovirus infections

C Sandoval,J Romero,S Llamas

doi:10.5424/sjar/200806s1-387

C Sandoval, J Romero + Show 1 more

Open Access

https://doi.org/10.5424/sjar/200806s1-387

Copy DOI

Abstract

Defective RNA molecules (D-RNAs) are being studied in several plant RNA virus groups. In the genus Bromovirus, D-RNAs have been described for Broad bean mottle virus (BBMV), they are formed by a single internal deletion in the RNA2 and have been generated de novo by serial passages. In contrast, in Brome mosaic virus (BMV) D-RNAs are generated by a single or double internal deletion in the RNA3 without serial passages in their hosts. In this work the external effects of the host and the growth temperature in the generation and accumulation of D-RNAs in BBMV, BMV and Cowpea chlorotic mottle virus (CCMV) are studied. The BBMV and BMV D-RNAs were generated and accumulated with or without serial passages of the viruses in different hosts and cultivars. Plants grown at 12, 16, 20 and 24 deg C in a growth chamber and in a greenhouse (22 +/- 5 deg C) generated D-RNAs after being inoculated with virusfree D-RNAs, with and without passages. The D-RNAs observed in BBMV and BMV presented some common characteristics: both were formed de novo after serial passages or without passages, their deletion borders had short repeated and palindrome sequences that favour recombination. In addition, growing inoculated plants at lower temperatures greatly facilitated the generation and accumulation of D-RNAs. The CCMV did not generate defective molecules in cowpea (Vigna unguiculata) and Nicotiana benthamiana plants after several serial passages or without passages. This is the first time that D-RNAs have been generated in BBMV without passages and BMV with serial passages.

Highlights

Los RNAs defectivos (D-RNAs) están siendo estudiados en diversos virus RNA de plantas
The RNA1 and RNA2 encode the 1a and 2a proteins required for virus replication (Kibertis et al, 1981), RNA3 encodes the 3a protein required for virus movement (Schmitz and Rao, 1996) and the coat protein which is synthesized from the subgenomic RNA4 by virus replicase from a promoter present in the (–) strand of RNA3 (Miller et al, 1985)
To continue these studies and to observe if broad bean plants could support the formation of defective interfering RNAs (D-RNAs) without passages, broad bean seedlings were inoculated with Broad bean mottle virus (BBMV) RNA that was free of D-RNAs and the plants were grown in a greenhouse

Summary

Introduction

Los RNAs defectivos (D-RNAs) están siendo estudiados en diversos virus RNA de plantas. In BBMV several RNA2 – derived D-RNAs have been characterized (Romero et al, 1993), they are generated de novo after serial passages and their presence reduced the accumulation of RNA2 of the helper virus. They exacerbated the severity of symptoms and have a negative effect on production, reducing yield by 50% (Romero et al, 1993; Pogany et al, 1995, 1997; Llamas et al, 2004; Sandoval et al, 2007). They were characterized and some external factors which affects its accumulation such as plant host, environment and temperature analysed

Methods

Results

Conclusion