Characterization of polyphenol oxidase changes induced by desiccation of Ramonda serbica leaves

Abstract

Resurrection plants are able to dehydrate/rehydrate rapidly without cell damage by a mechanism, the understanding of which may be of ecological importance in the adaptation of crop plants to dry conditions. The o-diphenol oxidase in Ramonda serbica Pan. & Petrov, a rare resurrection plant of the Balkan Peninsula, was characterized in respect to different isoforms, preferable substrates and specific inhibitors. Two anionic isoforms with pI 4.6 and 4.7 were separated from turgid leaves. Three additional anionic isoforms (pI 5.1, 5.3 and 5.6) and three neutral isoforms (pI from 6.8 to 7.4) were induced in desiccated leaves. Based on apparent K(m) values, the affinity for reducing substrates decreased as follows: methyl catechol > chlorogenic acid > 3,4-dihydroxyphenylalanine > caffeic acid > pyrogallol. Polyphenol oxidase (PPO) activity was specifically sensitive to diethyldithiocarbamate and also inhibited by KCN, DTT and salicylic hydroxamic acid but with no inhibitory effect of Na3N. Plants were subjected to drought-to-near complete water loss (approximately 2% relative water content, RWC) and several fold higher PPO activity was detected in desiccated leaves. Ramonda leaves contain high levels of phenolics, which decreased during drought. Rehydration of dry leaves from 2% RWC to 95% RWC led to transient inhibition of PPO in the first few hours. Within a day, the levels completely recovered to those determined in desiccated leaves. The finding of desiccation-induced high activity of PPO and new isoforms, which were also present in rehydrated turgid leaves, indicates a substantial role for PPO in the adaptation mechanism of resurrection plants to desiccation and also to the oxidative stress during rehydration.

Changes in Seed Germination Ability, Lipid Peroxidation and Antioxidant Enzyme Activities of Ginkgo biloba Seed during Desiccation

“…Many studies have confirmed that antioxidants such as SOD and POD were shown to have increased in response to desiccation [40,41], and may act as a "reservoir" and determine the period where a plant can remain desiccated before its viability is compromised [42]. During desiccation, the SOD and POD activity of G. biloba seed embryos were first reduced, then elevated to the highest value, before declining.…”

Characterization of oxidative and antioxidative events during dehydration and rehydration of resurrection plant Ramonda nathaliae

“…Although phylogenetically closely related, these plants differ in their ecological requirements (Stevanović et al 1991) and ploidy levels (Š iljak-Yakovlev et al 2008). Protective systems involved in the response to dehydration/ rehydration, such as changes of membrane lipids (Quartacci et al 2002), ascorbate and glutathione contents (Sgherri et al 2004), antioxidative enzyme activities (Veljović-Jovanović et al 2006;Veljović-Jovanović et al 2008), have been investigated in R. serbica but not in R. nathaliae. The objective of this work was to analyse some oxidative/antioxidative events in leaves of R. nathaliae during dehydration and rehydration.…”

A Sister Group Contrast Using Untargeted Global Metabolomic Analysis Delineates the Biochemical Regulation Underlying Desiccation Tolerance in Sporobolus stapfianus

“…Lastly, polyphenol oxidase, which catalyzes the oxidation of mono-and o-diphenols to o-diquinones, showed increased protein abundance and enzyme activity in the dehydrating leaves of several resurrection species (Jiang et al, 2007;VeljovicJovanovic et al, 2008). Polyphenols are powerful detoxifiers of toxic ROS and may function as antioxidants during the first few hours of rehydration (Veljovic-Jovanovic et al, 2008). Although we begin to grasp how resurrection plants respond to desiccation or rehydration, without a relevant comparison between the responses of sensitive and tolerant tissues, any insight into the adaptive processes remains simply speculative.…”