Roles of plant hormones in the regulation of host–virus interactions

Abstract

Hormones are tuners of plant responses to biotic and abiotic stresses. They are involved in various complicated networks, through which they modulate responses to different stimuli. Four hormones primarily regulate plant defence to pathogens: salicylic acid (SA), jasmonic acid (JA), ethylene (Et) and abscisic acid (ABA). In susceptible plants, viral infections result in hormonal disruption, which manifests as the simultaneous induction of several antagonistic hormones. However, these antagonistic hormones may exhibit some sequential accumulation in resistant lines. Virus propagation is usually restricted by the activation of the small interfering RNA (siRNA) antiviral machinery and/or SA signalling pathway. Several studies have investigated these two systems, using different model viruses. However, the roles of hormones other than SA, especially those with antagonistic properties, such as ABA, have been neglected. Increasing evidence indicates that hormones control components of the small RNA system, which regulates many processes (including the siRNA antiviral machinery and the microRNA system) at the transcriptional or post-transcriptional level. Consequently, cross-talk between the antagonistic SA and ABA pathways modulates plant responses at multiple levels. In this review, we summarize recent findings on the different roles of hormones in the regulation of plant-virus interactions, which are helping us to elucidate the fine tuning of viral and plant systems by hormones.

The effect of inoculation with arbuscular mycorrhizal fungus Rhizophagus irregularis on cytokinin content in a highly mycotrophic Medicago lupulina line under low phosphorus level in the soil

“…It was suggested that AM fungi enhanced sink strength and promoted photosynthesis due to ZR. Moreover, ZR was involved in transduction of nutritional signals, and thus, slowing down of the process of senescence in target plants (Alazem and Lin 2015). The origin of ZR in mycorrhized plants is still under discussion but there is some evidence that AM fungi might synthesize CK, as in axenic mycelial cultures (Barea and Azćon-Aguilar 1982).…”

Physiological, phenometric and productive changes in soybean crop due to the use of kinetin

“…The functions of these hormones include everything from promoting apical meristem growth to cell cycle regulation and nutrient mobilization, controlling senescence and the formation of root nodules in nitrogen-fixing plants (Zwack & Rashotte 2013, Cortleven & Schmülling 2015. Moreover, recent studies indicate that this hormone may modulate antioxidant metabolic pathways, reducing the stress level of plants (O'Brien & Benková 2013, Alazem & Lin 2015, Zwack & Rashotte 2015. Taken together, these functions demonstrate that using the hormone may cause changes that lead to a higher yield in plants.…”

Modulation of host plant immunity by Tobamovirus proteins

“…It was demonstrated that the majority of defence-related genes whose expression is increased during viral infections are responsive to salicylic acid (SA) (Huang et al, 2005). In addition to this, it was shown that SA plays a prominent role during plant-virus interactions (Nicaise, 2014;Alazem and Lin, 2015) and together with ROS act in a concerted manner to regulate the transcriptional responses to stress (Herrera-Vasquez et al, 2015). Considering the relevance of SA during viral infections and the cross-talk with ROS signalling pathways, in this section we summarize the most relevant findings that support the role of both signalling molecules during plant-viral interactions.…”