Systemic Acquired Resistance Mediated by the Ectopic Expression of Invertase: Possible Hexose Sensing in the Secretory Pathway.

Abstract

Systemic acquired resistance (SAR) has been reported to be associated with lesion-mimic mutants. Tobacco plants expressing vacuolar and apoplastic yeast-derived invertase (vaclnv and cwlnv, respectively) develop spontaneous necrotic lesions similar to hypersensitive responses caused by avirulent pathogens. Therefore, SAR and metabolic alterations leading to the activation of defense-related responses were studied in these plants. Defense-related gene transcripts, callose content, peroxidase activities, and levels of salicylic acid were found to be elevated. The defense reactions were accompanied by increased resistance toward potato virus Y and were measured as decreased vira1 spreading and reduced multiplication in systemic leaves of the transgenic plants. Interestingly, the accumulation of pathogenesis-related (PR) protein transcripts (PR-Q) and repression of photosynthstic gene transcripts (chlorophyll a/b binding protein) were inversely correlated and required the same threshold leve1 of hexoses for induction and repression. Expression of a cytosolic yeast-derived invertase in transgenic tobacco plants with equally increased levels of sugars neither displayed SAR responses nor showed decreased levels of photosynthetic genes. It is suggested that hexose sensing in the secretory pathway is essential for mediating the activation of defense-related genes as well as repression of photosynthetic genes in vaclnv and cwlnv plants.

Sucrose and invertases, a part of the plant defense response to the biotic stresses

“…In tobacco plants overexpressing a yeast invertase in the apoplast or in the vacuole, the increase of callose deposition was comparable to that observed in wild type plants infected with potato virus Y (Herbers et al, 1996). These results were consistent with a positive regulation of callose deposition by GIF1 in rice after infection by both, bacterial and fungal pathogens (Sun et al, 2013), leading to a regulation mediated by CWI activity.…”

Targeting the AtCWIN1 Gene to Explore the Role of Invertases in Sucrose Transport in Roots and during Botrytis cinerea Infection

“…CWIN activity has been associated with plant resistance and defense mechanisms during several biotrophic and hemibiotrophic interactions (Herbers et al, 1996; Essmann et al, 2008a; Bonfig et al, 2010; Sun et al, 2014). The absence of Botrytis -induced CWIN activity in cwin1-1 (Figure 4A) prompted us to investigate the biological importance of AtCWIN1 in the outcome of B. cinerea infection.…”

“…For the former, these sugars represent a source of energy allowing growth and reproduction whereas for the latter, sugars can fuel the costly induction of defense mechanisms and act as signaling molecules to regulate defense gene expression (Herbers et al, 1996; Roitsch, 1999; Bolton, 2009; Bolouri Moghaddam and Van den Ende, 2012). The competition for available sugars is crucial for the outcome of the interaction (Lemoine et al, 2013).…”

Regulation of Cell Wall-Bound Invertase in Pepper Leaves by Xanthomonas campestris pv. vesicatoria Type Three Effectors

“…Hence, a fast increase of hexoses appeared to be important for an efficient and successful defense response. This is supported by the observation that high levels of sugars by expressing a yeast invertase in either the apoplast or in the vacuole of transgenic tobacco plants mediated resistance against potato virus Y [14], [20]. In contrast, repression of cw-Inv activity in tobacco using an RNAi approach resulted in a lower amount of available hexoses and caused an impaired defense response following infection with Phytophthora nicotianae [13].…”