Phyto-hormonal regulation of local and systemic defense and photosynthetic-responses to herbivore perception in Nicotiana attenuata

Abstract

Evolution led to the development of mechanisms for the recognition of herbivores in plants (the doors of perception). These mechanisms by themselves induce changes in plants that allows them to respond adequately to the threat by the herbivore. These changes not only include mechanisms of defense, but also changes in the primary metabolism and physiology of plants. The metabolic and physiological changes are the result of the regulation by various signals, in which hormones play an important role. In this work, I described the regulation of metabolic and physiological changes by the phytohormones clases cytokinins (CK) and jasmonates (Jas) after perception of herbivore elicitors of Manduca sexta oral secretions (OS) in Nicotiana attenuata plants. I show for the first time the regulation of endogenous CK in treated (local) leaves and systemic tissues after wounding and perception of herbivore elicitors (OS-elicitation) in N. attenuata and Arabidopsis. These changes in CK moieties were accompanied by changes in the expression of signaling and biosynthetic genes, but where only affected partially by jasmonates biosynthesis and signaling. Conversely, I found that CK induce changes in the accumulation of jasmonic acid (JA), but not in JA-isoleucine (JA-Ile) after OS-elicitation in local leaves. I argue that the change in the levels of JA induced by CK signaling is due to a shift in the biosynthetic pathway of JAs towards the synthesis of terpene-volatiles, also modified by CK signaling. I also found that CK signaling through CK receptors (NaCHK2 and NaCHK3) positively affected the accumulation defense metabolites and protease inhibitors activity induced by herbivore elicitation. But it remains to be answered if the CK induced changes in defenses is a direct effect of CK signaling or induced by the observed changes in JAs. ...