Response of transglutaminase activity and bound putrescine to changes in light intensity under natural or controlled conditions in Quercus ilex leaves

Abstract

In order to further study a previously observed relationship between polyamine (PA) content and changes in irradiation, we examined the level of free and bound PAs, the activity of transglutaminase (TGase, EC 2.3.2.13) and chlorophyll fluorescence in holm oak (Quercus ilex L.) leaves in response to different levels of light intensity and amount. A diurnal trend of free and bound putrescine (F-Put and B-Put, respectively) and TGase activity was observed in plants under natural conditions in the forest, with the highest value corresponding to the maximum light intensity and amount of light received by the leaves. In another set of experiments, potted Q. ilex plants in experimental fields were subjected to a range of periods of natural photosynthetic photon flux density (PPFD) by covering or not covering the whole trees. Under a natural photoperiod (uncovered leaves), B-Put content and TGase activity paralleled the diurnal PPFD pattern, reaching a maximum at the highest PPFD; prior to this maximum, free PAs showed a significant rise. Plants that were in darkness until midday and suddenly exposed to high light intensity showed enhanced TGase activity, resulting in the maximum accumulation of B-Put. The involvement of the accumulation of B-Put reflected in the changes of the B-Put/bound spermidine ratio during the photoprotective responses to high light stress in forest plants is discussed in relation to the chlorophyll fluorescence parameters observed.

Oxidative stress induced in tobacco leaves by chloroplast over-expression of maize plastidial transglutaminase

“…In chloroplasts, TGases can interact with photosystem II proteins (LHCII, CP29, CP26, CP24), catalysing their modification by polyamines in a light-dependent way (Della Mea et al 2004). Also, in sunlight conditions, TGases play a role in photoprotective processes, increasing activity during maximal light intensity (Pintó-Marijuan et al 2007). It is known that environmental stresses may damage cells either directly or indirectly, through the formation of reactive oxygen species (ROS) (Asada 1999;Buchanan et al 2000).…”

Role of Plastid Transglutaminase in LHCII Polyamination and Thylakoid Electron and Proton Flow

“…The heterologous expression of TGZ in E. coli cells indicates that the native substrate preferences in the recombinant TGZp were maintained and also that the enzyme activity was light dependent only in the case when light-grown plant protein substrates were used [17], [18]. Taking into account all the described results, it has been hypothesized that TGases are implicated in the photosynthetic process [14], [15], [19]. First evidence for a role of plastidial TGase in the thylakoids 3D architecture comes from tobacco over expressing maize TGase (TGZ) [20].…”

“…An important step in elucidating the role of plastidal TGase was the isolation for the first time in plants of two related complementary maize cDNA clones, tgz15 and tgz21 , encoding active maize TGase (TGZ) [13], [14]. Their expression was dependent on length of light exposure, indicating a role in adaptation to different light environmental conditions, including natural habitats [15]. Proteomic studies indicates that maize chloroplastic TGase is a peripheral thylakoid protein forming part of a specific PSII protein complex which includes LHCII, ATPase and PsbS proteins [16].…”

Transglutaminase is Involved in the Remodeling of Tobacco Thylakoids

“…Proteomic studies indicates that plastidial maize TGase is a peripheral thylakoid protein forming part of a specific PSII protein complex which includes LHCII, ATPase and PsbS proteins, its expression pattern changing according to chloroplast developmental stage and light regime (Campos et al 2010). Tacking into account all the described results, it has been hypothesized that TGases are implicated in the photosynthetic process (Villalobos et al 2004;Pintó-Marijuan et al 2007;Serafini-Fracassini & Del Duca, 2008).…”

“…An important step for the elucidation of the plastidal TGase role in plants was the isolation for the first time in plants of two related complementary maize DNA clones, tgz15 and tgz21, encoding active maize TGase (Torné et al 2002;Villalobos et al 2004). Interestingly, their expression is dependent on the duration of light exposure, indicating a role for adaptation in different light environmental conditions including natural habitats (Pintó-Marijuan et al 2007;Carvajal et al 2007Carvajal et al -2011. Proteomic studies indicates that plastidial maize TGase is a peripheral thylakoid protein forming part of a specific PSII protein complex which includes LHCII, ATPase and PsbS proteins, its expression pattern changing according to chloroplast developmental stage and light regime (Campos et al 2010).…”