Comparative cytopathology of Crinivirus infections in different plant hosts

Abstract

SummaryWe used transmission electron microscopy to compare the cytopathology induced in plants by five criniviruses (genus Crinivirus; Lettuce infectious yellows virus (LIYV), Cucurbit yellow stunting disorder virus (CYSDV), Tomato infectious chlorosis virus (TICV), Tomato chlorosis virus (ToCV) and Beet pseudo‐yellows virus (BPYV) (Hartono et al., 2003)). We also compared the patterns of infection for plants and mesophyll protoplasts infected by LIYV and Beet yellows virus (BYV), type members of genera Crinivirus and Closterovirus, respectively. The main cytopathological effects induced in plants by criniviruses were common in young leaves and included alterations of the chloroplasts and the presence of BYV‐type inclusion bodies in companion cells. Virus‐like particles were present in sieve tubes and vascular parenchyma cells as scattered particles, or in companion cells as large masses forming cross‐banded inclusions. Depending on the virus and the plant, it was possible to find virions or virus‐like particles out of the phloem cells, but only in cells of the bundle sheath. Virion‐like particles were never found outside of the vascular tissue. Accumulation of electron‐dense material at the plasmalemma was common for criniviruses, but only LIYV infections produced characteristic conical electron‐dense plasmalemma deposits (PDs). The LIYV‐induced PDs have a crystalline‐like structure and were found at the internal side of plasmalemma.