Novel compounds that enhance Agrobacterium-mediated plant transformation by mitigating oxidative stress

Abstract

Agrobacterium tumefaciens caused tissue browning leading to subsequent cell death in plant transformation and novel anti-oxidative compounds enhanced Agrobacterium -mediated plant transformation by mitigating oxidative stress. Browning and death of cells transformed with Agrobacterium tumefaciens is a long-standing and high impact problem in plant transformation and the agricultural biotechnology industry, severely limiting the production of transgenic plants. Using our tomato cv. MicroTom transformation system, we demonstrated that Agrobacterium caused tissue browning (TB) leading to subsequent cell death by our correlation study. Without an antioxidant (lipoic acid, LA) TB was severe and associated with high levels of GUS transient expression and low stable transformation frequency (STF). LA addition shifted the curve in that most TB was intermediate and associated with the highest levels of GUS transient expression and STF. We evaluated 18 novel anti-oxidative compounds for their potential to enhance Agrobacterium-mediated transformation, by screening for TB reduction and monitoring GUS transient expression. Promising compounds were further evaluated for their effect on MicroTom and soybean STF. Among twelve non-antioxidant compounds, seven and five significantly (P < 0.05) reduced TB and increased STF, respectively. Among six antioxidants four of them significantly reduced TB and five of them significantly increased STF. The most efficient compound found to increase STF was melatonin (MEL, an antioxidant). Optimal concentrations and stages to use MEL in transformation were determined, and Southern blot analysis showed that T-DNA integration was not affected by MEL. The ability of diverse compounds with different anti-oxidative mechanisms can reduce Agrobacterium-mediated TB and increase STF, strongly supporting that oxidative stress is an important limiting factor in Agrobacterium-mediated transformation and the limiting factor can be controlled by these compounds at different levels.

Melatonin production in Escherichia coli by dual expression of serotonin N-acetyltransferase and caffeic acid O-methyltransferase

“…Treating various plant species with low concentrations of exogenous melatonin (<1 μM) promotes root and coleoptile growth (Hernández-Ruiz et al 2005;Chen et al 2009) and ameliorates stress injury due to salt , alkaline soda stress (Liu et al 2015), drought (Meng et al 2014), and oxidative stress (Dan et al 2015). In addition to mitigating effects on abiotic stressors, melatonin participates in the response to pathogen attack as a signaling molecule by enhancing salicylic acid levels, resulting in resistance to infection (Lee et al , 2015.…”

Low melatonin production by suppression of either serotonin N‐acetyltransferase or N‐acetylserotonin methyltransferase in rice causes seedling growth retardation with yield penalty, abiotic stress susceptibility, and enhanced coleoptile growth under anoxic conditions

“…As sessile organisms, plants are challenged by a number of threating sources of stress, categorized as abiotic or biotic. Among many abiotic stresses, melatonin is positively implicated in mitigating plant injury by modulating and promoting the endogenous defense mechanisms against cold , heat , drought , UV light , reactive oxygen species , and osmotic shock . Apart from these defensive roles in plants, melatonin is also known to participate in promoting root formation and seedling growth , as well as plant ripening and the senescence processes .…”

2‐Hydroxymelatonin promotes the resistance of rice plant to multiple simultaneous abiotic stresses (combined cold and drought)

“…Melatonin has several functions in plant growth and development including rhizogenesis, photosynthesis, senescence, and seedling growth from germination onward . Plant stress responses include defense mechanisms against a range of potentially debilitating biotic and abiotic factors such as pathogens, cold, heat, drought, salinity, and oxidative stresses . The modulatory role of melatonin in all of these functions is closely associated with multiple changes in gene expression, which are the result of melatonin acting alone or in combination with environmental stressors .…”

“…[11][12][13][14] Plant stress responses include defense mechanisms against a range of potentially debilitating biotic and abiotic factors such as pathogens, [15][16][17] cold, 18,19 heat, 20 drought, 21,22 salinity, 23,24 and oxidative stresses. 25,26 The modulatory role of melatonin in all of these functions is closely associated with multiple changes in gene expression, which are the result of melatonin acting alone or in combination with environmental stressors. 27 Thus, melatonin acts as a modulator of gene expression 2,28 or as a signaling molecule that triggers extensive transcriptional reprogramming.…”