Leaf-associated bacteria from transgenic white poplar producing resveratrol-like compounds: isolation, molecular characterization, and evaluation of oxidative stress tolerance

Abstract

The aim of this study was the isolation and characterization of the culturable bacteria inhabiting the leaves of transgenic white poplars (Populus alba L. 'Villafranca') engineered with the StSy gene for the production of resveratrol-like compounds. Resveratrol glucosides are available in small amounts from natural sources or by expensive chemical synthesis procedures. An alternative approach for the large-scale production of these relevant pharmaceuticals is the use of transgenic plants as bioreactors, although the occurrence of novel molecules in plants growing under field conditions might interfere, to some extent, with the associated microbial population. Both epiphytes and endophytes were isolated from the leaves of 2 StSy transgenic lines producing resveratrol glucosides and from an untransformed plant line grown in a greenhouse. Eleven isolates were recovered and classified as members of the genus Bacillus by 16S rDNA-based analysis. In addition, 2 isolates were classified as members of the Curtobacterium and Kocuria genera, respectively. Tolerance to hydrogen peroxide, UV-C, and paraquat was evaluated, as were the swimming and swarming motility of the leaf-associated bacteria. Interestingly, the isolates recovered from transgenic tissues showed the ability to withstand oxidative stress compared with isolates recovered from the untransformed poplar line. In vitro bioassays showed that trans-resveratrol inhibited both the swarming and swimming motilities in all the tested bacteria. The effects of trans-resveratrol on flagellin production, required for motility, were also investigated by immunoblot analysis.

Radioprotective and Antioxidant Effect of Resveratrol in Hippocampus by Activating Sirt1

“…In contrast, inhibition of Sirt1, such as with nicotinamide, can block proliferation and lead to apoptosis in leukemic cells, possibly through p53-dependent and independent mechanisms [24]. Furthermore, agents such as Sirtinol that inhibit Sirt1 activity can be detrimental to neurons during oxidative stress [25] while the use of the specific small-molecule inhibitor of Sirt1 EX527 [26] can block HDAC activity and increase vascular injury during oxidative stress, suggesting that an endogenous level of Sirt1 is required for vascular protection [23]. …”

Spore-forming bacteria in soil cultivated with GM white poplars: Isolation and characterization

“…We have explored the response to purified trans-resveratrol in bacteria recovered from leaves of GM white poplars expressing the StSy transgene and all the isolates, members of the genus Bacillus, were sensitive to trans-resveratrol (Balestrazzi et al 2009a). …”

“…Although several examples of GM plants expressing the StSy gene responsible for resveratrol production have been reported (e.g., Delaunois et al 2009), only a few studies related to their environmental impact at the soil level have been described (Bonadei et al 2009;Balestrazzi et al 2009a).…”

DNA extraction from soil: comparison of different methods using spore-forming bacteria and theswrAA gene as indicators

“…Aim of this study was to develop an improved protocol for DNA extraction and purification from a humic acid-rich soil used to establish two extensive greenhouse trials with transgenic white poplars (Balestrazzi et al, 2007(Balestrazzi et al, , 2008(Balestrazzi et al, , 2009a(Balestrazzi et al, , 2009bBonadei et al, 2009).…”

“…This soil has been used for the cultivation of transgenic white poplars engineered with the StSy gene from Vitis vinifera and with the bar gene from Streptomyces hygroscopicus, respectively, in greenhouse trials (Balestrazzi et al, 2007(Balestrazzi et al, , 2008(Balestrazzi et al, , 2009a(Balestrazzi et al, , 2009bBonadei et al, 2009). In the GM poplars expressing the StSy gene encoding stilbene synthase, responsible for resveratrol biosynthesis, the amount of resveratrol-like compounds was in the range 180-210 mg kg -1 fresh leaf tissue (Balestrazzi et al, 2009b). As for the herbicide-tolereant poplars, the genetically modified poplars were tolerant to intense and repeated glufosinate ammonium treatments, maintaining an intact shoot sprouting and a good height increment (Balestrazzi et al, unpublished data).…”