Abstract
Plant-virus interactions are frequently influenced by elevated temperature, which often increases susceptibility to a virus, a scenario described for potato cultivar Chicago infected with potato virus Y (PVY). In contrast, other potato cultivars such as Gala may have similar resistances to PVY at both normal (22 °C) and high (28 °C) temperatures. To elucidate the mechanisms of temperature-independent antivirus resistance in potato, we analysed responses of Gala plants to PVY at different temperatures using proteomic, transcriptional and metabolic approaches. Here we show that in Gala, PVY infection generally upregulates the accumulation of major enzymes associated with the methionine cycle (MTC) independently of temperature, but that temperature (22 °C or 28 °C) may finely regulate what classes accumulate. The different sets of MTC-related enzymes that are up-regulated at 22 °C or 28 °C likely account for the significantly increased accumulation of S-adenosyl methionine (SAM), a key component of MTC which acts as a universal methyl donor in methylation reactions. In contrast to this, we found that in cultivar Chicago, SAM levels were significantly reduced which correlated with the enhanced susceptibility to PVY at high temperature. Collectively, these data suggest that MTC and its major transmethylation function determines resistance or susceptibility to PVY.
Highlights
Plant viruses are responsible for a broad range of diseases which cause severe crop losses and are a serious threat to sustainable agriculture
To explore the underlying mechanisms responsible for resistance to potato virus Y (PVY) in Gala plants, we used iTRAQ-based quantitative comparative proteomic technology. iTRAQ analysis was conducted at an early time point (8 dpi), when PVY starts to invade plants systemically, and at a 14 dpi time point, which represents a later stage of infection when metabolic changes may be highly pronounced
We found that plant responses to PVY in Chicago are closely related to the methionine cycle (MTC) [5] and showed that the increased susceptibility of Chicago plants to PVY at higher temperature was associated with the orchestrated down-regulation of levels of major enzymes involved in the MTC (MS, S-adenosylmethionine synthase 2 (SAMS), SAHH) and MTC-related folate cycle (SHM and MTHFR) at 28 ◦C
Summary
Plant viruses are responsible for a broad range of diseases which cause severe crop losses and are a serious threat to sustainable agriculture. The increasingly frequent emergence and re-emergence of viral diseases is often associated with the high capacity of viruses to rapidly evolve, a situation worsened by global climate change, which can influence vector transmission and plant susceptibility to infection [1]. When the virus can successfully infect host plants, this is known as a compatible interaction [2]. While there is an orchestrated cross-talk of virus components with host plant machinery during such interactions, there can be an associated dynamic remodelling of host metabolism during the infection process [3]. A major metabolic process affected by plant virus infections is the methionine cycle (MTC) [4,5]
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