Expression of the Beet necrotic yellow vein virus p25 protein induces hormonal changes and a root branching phenotype in Arabidopsis thaliana

Abstract

The RNA-3-encoded p25 protein was previously characterized as one of the major symptom determinants of the Beet necrotic yellow vein virus. Previous analyses reported the influence of the p25 protein in root proliferation phenotype observed in rhizomania disease on infected sugar beets (Beta vulgaris). A transgenic approach was developed, in which the p25 protein was constitutively expressed in Arabidopsis thaliana Columbia (Col-0) ecotype in order to provide new clues as to how the p25 protein might promote alone disease development and symptom expression. Transgenic plants were characterized by Southern blot and independent lines carrying single and multiple copies of the transgene were selected. Mapping of the T-DNA insertion was performed on the monocopy homozygote lines. P25 protein was localized both in the nucleus and in the cytoplasm of epidermal and root cells of transgenic plants. Although A. thaliana was not described as a susceptible host for BNYVV infection, abnormal root branching was observed on p25 protein-expressing A. thaliana plants. Moreover, these transgenic plants were more susceptible than wild-type plants to auxin analog treatment (2,4-D) but more resistant to methyl jasmonate (MeJA), abscisic acid (ABA) and to lesser extend to salicylic acid (SA). Hormonal content assays measuring plant levels of auxin (IAA), jasmonate (JA) and ethylene precursor (ACC) revealed major hormonal changes. Global transcript profiling analyses on roots displayed differential gene expressions that could corroborate root branching phenotype and stress signaling modifications.

Variation in Virus Symptom Development and Root Architecture Attributes at the Onset of Storage Root Initiation in ‘Beauregard’ Sweetpotato Plants Grown with or without Nitrogen

“…Such findings can lead directly to the development and testing of management practices for improved economic yields, water use efficiency and nutrient foraging. Recent work in model systems has demonstrated that virus infections can lead to alterations in lateral root development [22], [23], [24]. These findings provide evidence about the potential influence of biotic factors on root architecture development.…”

“…In the past, information on morphological, hormonal, and molecular characterizations of virus infection on roots have been limited [34], [35], but new findings are beginning to reveal the integrative role of auxin in mediating virus effects on root architecture. For example, Arabidopsis plants that were transformed to express the Beet necrotic yellow vein virus p25 protein showed abnormal root branching, accompanied by significant changes in the levels of auxin, jasmonic acid and ethylene precursor, ACC [24]. In another study, Cucumber mosaic virus -infected Arabidopsis root growth patterns were accompanied by significant changes in indole-3-acetic acid (IAA), trans -zeatin riboside and dihydrozeatin riboside [25].…”

A Viral Noncoding RNA Complements a Weakened Viral RNA Silencing Suppressor and Promotes Efficient Systemic Host Infection

“…The smaller RNAs (RNA3, RNA4, and, when present, RNA5) are dispensable for infection of laboratory hosts upon mechanical inoculation but are required for the natural infection of Beta species and for transmission of the virus. RNA3 influences symptom expression in host plants through its p25 protein [10,11]. RNA3 is also essential for BNYVV long-distance movement in Beta species, but this does not require p25, as p25-deficient RNA3 still moves long distances [12].…”

Plant Virus Infection and the Ubiquitin Proteasome Machinery: Arms Race along the Endoplasmic Reticulum

“…The classic symptoms of rhizomania are expansive numbers of secondary roots that give the main taproot a bearded appearance. The Gilmer laboratory transgenically expressed the BNYVV P25 protein in Arabidopsis and plants showed more lateral roots than the non-transgenic controls, had higher levels of auxin, and were more responsive to exogenous applications of 2,4-Dichlorophenoxyacetic acid (2,4-D; an auxin analog) [57]. Three genes encoding F-box proteins were upregulated in these transgenic Arabidopsis plants.…”