Genetic engineering of glycinebetaine synthesis in tomato protects seeds, plants, and flowers from chilling damage

Abstract

Tomato (Lycopersicon esculentum Mill.) plants, which normally do not accumulate glycinebetaine (GB), are susceptible to chilling stress. Exposure to temperatures below 10 degrees C causes various injuries and greatly decreases fruit set in most cultivars. We have transformed tomato (cv. Moneymaker) with a chloroplast-targeted codA gene of Arthrobacter globiformis, which encodes choline oxidase to catalyze the conversion of choline to GB. These transgenic plants express codA and synthesize choline oxidase, while accumulating GB in their leaves and reproductive organs up to 0.3 and 1.2 micromol g(-1) fresh weight (FW), respectively. Their chloroplasts contain up to 86% of total leaf GB. Over various developmental phases, from seed germination to fruit production, these GB-accumulating plants are more tolerant of chilling stress than their wild-type counterparts. During reproduction, they yield, on average, 10-30% more fruit following chilling stress. Endogenous GB contents as low as 0.1 micromol g(-1) FW are apparently sufficient to confer high levels of tolerance in tomato plants, as achieved via transformation with the codA gene. Exogenous application of either GB or H2O2 improves both chilling and oxidative tolerance concomitant with enhanced catalase activity. These moderately increased levels of H2O2 in codA transgenic plants, as a byproduct of choline oxidase-catalyzed GB synthesis, might activate the H2O2-inducible protective mechanism, resulting in improved chilling and oxidative tolerances in GB-accumulating codA transgenic plants. Thus, introducing the biosynthetic pathway of GB into tomato through metabolic engineering is an effective strategy for improving chilling tolerance.

Redox potentials of primary electron acceptor quinone molecule (Q A ) − and conserved energetics of photosystem II in cyanobacteria with chlorophyll a and chlorophyll d

“…Titration. All experiments were performed in the presence of betaine, a natural osmolyte, at pH 7.0, because it has previously been shown that PS II preparations are more stable in the presence of 1 M glycine betaine (12,(38)(39)(40)(41)(42)(43). Details of the physiological conditions used for various species are summarized in SI Materials and Methods, Figs.…”

Genetic engineering of glycine betaine biosynthesis to enhance abiotic stress tolerance in plants

“…In COD-transgenic tomato plants, GB showed an effect on chilling stress tolerance (Park et al 2004). Despite very low GB accumulation, the transgenic tomato plants exhibited enhanced chilling tolerance at all developmental stages, from seed germination to the reproductive stage.…”

“…Despite very low GB accumulation, the transgenic tomato plants exhibited enhanced chilling tolerance at all developmental stages, from seed germination to the reproductive stage. The enhanced chilling-stress tolerance in the presence of very low GB levels may be due to the very low threshold level of endogenous GB (Ͼ0.1 mmol g Ϫ1 fw) that is sufficient to provide full protection against chilling stress in transgenic tomato (Park et al 2004). In addition, both cytosolic and chloroplast-targeted COD-transgenic tomato plants showed a correlation between the accumulated GB in these compartments and the degree of tolerance to low temperature, salt, and oxidative stresses (Park et al 2007a).…”

Reactive oxygen species, ABA and nitric oxide interactions on the germination of warm-season C4-grasses

“…For switchgrass seeds, published colorimetric methods for determining tissue peroxide levels (Park et al 2004;Cheeseman 2006) were unsuccessful primarily due to a high background arising from extractable components that interfered with these assays. Attempts to clean extracts by passage through normal or C-18 reverse phase matrices conditioned with phosphate buVer containing 5 mM KCN (Cheeseman 2006) were also unsuccessful.…”