Suppression of cell wall-related genes associated with stunting of Oryza glaberrima infected with Rice tungro spherical virus.

Bernard O Budot,Israel Dave V Ambita,Jaymee R Encabo,Ramil Mauleon,Genelou A Atienza-Grande,Il-Ryong Choi,Victor J Ulat,Shoshi Kikuchi,Kouji Satoh,Hiroaki Kondoh

doi:10.3389/fmicb.2014.00026

Bernard O Budot, Israel Dave V Ambita + Show 8 more

Open Access

https://doi.org/10.3389/fmicb.2014.00026

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Abstract

Rice tungro disease is a complex disease caused by the interaction between Rice tungro bacilliform virus and Rice tungro spherical virus (RTSV). RTSV alone does not cause recognizable symptoms in most Asian rice (Oryza sativa) plants, whereas some African rice (O. glaberrima) plants were found to become stunted by RTSV. Stunting of rice plants by virus infections usually accompanies the suppression of various cell wall-related genes. The expression of cell wall-related genes was examined in O. glaberrima and O. sativa infected with RTSV to see the relationship between the severity of stunting and the suppression of cell wall-related genes by RTSV. The heights of four accessions of O. glaberrima were found to decline by 14–34% at 28 days post-inoculation (dpi) with RTSV, whereas the height reduction of O. sativa plants by RTSV was not significant. RTSV accumulated more in O. glaberrima plants than in O. sativa plants, but the level of RTSV accumulation was not correlated with the degree of height reduction among the four accessions of O. glaberrima. Examination for expression of genes for cellulose synthase A5 (CESA5) and A6 (CESA6), cellulose synthase-like A9 (CSLA9) and C7, and α-expansin 1 (expansin 1) and 15 precursors in O. glaberrima and O. sativa plants between 7 and 28 dpi with RTSV showed that the genes such as those for CESA5, CESA6, CSLA9, and expansin 1were more significantly suppressed in stunted plants of O. glaberrima at 14 dpi with RTSV than in O. sativa, suggesting that stunting of O. glaberrima might be associated with these cell wall-related genes suppressed by RTSV. Examination for expression of these genes in O. sativa plants infected with other rice viruses in previous studies indicated that the suppression of the expansin 1 gene is likely to be a signature response commonly associated with virus-induced stunting of Oryza species. These results suggest that stunting of O. glaberrima by RTSV infection might be associated with the suppression of these cell wall-related genes at the early stage of infection with RTSV.

Highlights

Rice tungro disease (RTD) is one of the major constraints to rice production in South and Southeast Asia (Azzam and Chancellor, 2002)
RTD is a composite disease caused by two taxonomically unrelated viruses, Rice tungro bacilliform virus (RTBV) and Rice tungro spherical virus (RTSV) both transmitted by green leafhoppers (GLH) (Hull, 1996)
We examined the relationship between the severity of stunting and the expression of six cell wall-related genes in O. glaberrima infected with RTSV to see whether stunting of O. glaberrima is associated with the capability of RTSV to suppress the expression of cell wall-related genes

Summary

Introduction

Rice tungro disease (RTD) is one of the major constraints to rice production in South and Southeast Asia (Azzam and Chancellor, 2002). RTBV is a plant pararetrovirus belonging to the family Caulimoviridae, genus Tungrovirus, with a circular, double-stranded DNA genome encapsidated in bacilliform particles (Fauquet et al, 2005). RTSV is the type member of the Sequiviridae family, genus Waikavirus, having a singlestranded polyadenylated plus-sense RNA genome encapsidated in polyhedral particles (Choi, 2008). Asian rice (Oryza sativa) plants infected with both RTBV and RTSV usually show symptoms such as severe stunting, yellowing of the leaves, and reduced tillering (Azzam and Chancellor, 2002).

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