Abstract
We investigated the roles of two Ferrochelatases (FCs), which encode the terminal enzyme for heme biosynthesis, in drought and oxidative stress tolerance in model cereal plant barley (Hordeum vulgare). Three independent transgenic lines ectopically overexpressing either barley FC1 or FC2 were selected and evaluated under well-watered, drought, and oxidative stress conditions. Both HvFC1 and HvFC2 overexpressing transgenics showed delayed wilting and maintained higher photosynthetic performance relative to controls, after exposure to soil dehydration. In each case, HvFC overexpression significantly upregulated the nuclear genes associated with detoxification of reactive oxygen species (ROS) upon drought stress. Overexpression of HvFCs, also suppressed photo-oxidative damage induced by the deregulated tetrapyrrole biosynthesis mutant tigrinad12. Previous studies suggest that only FC1 is implicated in stress defense responses, however, our study demonstrated that both FC1 and FC2 affect drought stress tolerance. As FC-derived free heme was proposed as a chloroplast-to-nuclear signal, heme could act as an important signal, stimulating drought responsive nuclear gene expression. This study also highlighted tetrapyrrole biosynthetic enzymes as potential targets for engineering improved crop performance, both in well-watered and water-limited environments.
Highlights
Drought is one of the major abiotic stress factors that adversely affects plant growth and limits crop yield [1]
A similar trend, albeit not statistically significant, was observed between HvFC2 transgenics and controls. These findings indicated that the higher leaf relative water content (RWC) was unlikely to be a consequence of reduced gs for HvFC1 and HvFC2 overexpressing transgenics
Similar to HvFC1 transgenics, Superoxide dismutase (Sod) was transcriptionally upregulated in HvFC2 transgenics, after 8 days of exposure to drought stress. These findings showed that both Ferrochelatase results in (FC) isoforms had the capacity to modulate nuclear encoded transcription of reactive oxygen species (ROS) detoxification enzymes, upon drought stress
Summary
Drought is one of the major abiotic stress factors that adversely affects plant growth and limits crop yield [1]. Improving drought tolerance of major crops such as cereals is a primary objective for plant breeding. Improved crop performance under water-limited conditions is necessary to satisfy food demands that are a consequence of a growing world population. The incidence and severity of drought events in many rain-fed cereal growing areas is likely to increase in the face of a changing climate. Photosynthesis is a primary cellular process that is directly affected by cellular water status [2]. Drought stress and the consequent reduction in cellular water status significantly reduces photosynthetic rate, by limiting CO2 diffusion through the stomata, and potentially induces
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