Presentation Information
[P03-445]Salt tolerance of transgrafted plants using codA-expressing rootstocks
○Hitomi Watanabe1, Taira Miyahara1, Hiroaki Kodama1 (1. Chiba Univ. (Japan))
Keywords:
transgrafting,salt stress,glycine betaine,transgenic rootstock
Salt stress is one of the major abiotic factors limiting plant growth and sustainable agricultural productivity. Glycine betaine (GB) is a compatible solute and an effective osmoprotectant that stabilizes proteins, membranes, and the photosynthetic apparatus, thereby mitigating oxidative damage under salt stress conditions. However, many crops, including tobacco, accumulate only low levels of GB. Although ectopic expression of GB biosynthetic genes enhances salt stress tolerance, constitutive GB accumulation throughout the whole plant often negatively affects plant growth.
Transgrafting, which combines genetically modified (GM) rootstocks with non-GM scions, has potential as a strategy to confer stress tolerance to non-GM scions without direct genetic modification. In this study, we examined whether transgrafting using rootstocks engineered for ectopic GB synthesis could modify salt stress responses in non-GM scions. Nicotiana tabacum plants were transformed with a chloroplast-targeted bacterial choline oxidase gene (codA) to enable GB biosynthesis. Under salt stress (200 mM NaCl treatment), codA-transgenic plants accumulated GB, exhibited enhanced antioxidant enzyme activities, and showed reduced accumulation of reactive oxygen species compared with wild-type (WT) plants. However, chlorophyll content in GB transgenic plants decreased under both control and salt stress conditions, and sodium ion concentrations were comparable to those in WT plants.
To assess the effects of transgrafting, WT scions were grafted onto codA-expressing rootstocks. Under salt stress conditions, WT scions of the transgrafted plants accumulated GB, exhibited enhanced antioxidant enzyme activities, and showed reduced levels of reactive oxygen species. Although sodium ion accumulation was comparable to that in salt-treated control WT homografts, chlorophyll content was maintained at levels similar to those of the control WT homografts, indicating that the growth-related drawbacks associated with GB accumulation were mitigated.
Transcriptomic profiles of non-GM scions grafted onto codA-transformed rootstocks were clearly distinct from those of control scions in WT homografts. Upregulated genes were enriched in stress-responsive and antioxidant-related pathways, whereas genes associated with photosynthesis and water transport processes tended to be downregulated.
Collectively, these findings demonstrate that transgrafting with codA-expressing rootstocks systemically alters physiological and transcriptional responses, partially conferring salt stress tolerance to non-transgenic scions without inducing GB-associated chlorophyll reduction.
Transgrafting, which combines genetically modified (GM) rootstocks with non-GM scions, has potential as a strategy to confer stress tolerance to non-GM scions without direct genetic modification. In this study, we examined whether transgrafting using rootstocks engineered for ectopic GB synthesis could modify salt stress responses in non-GM scions. Nicotiana tabacum plants were transformed with a chloroplast-targeted bacterial choline oxidase gene (codA) to enable GB biosynthesis. Under salt stress (200 mM NaCl treatment), codA-transgenic plants accumulated GB, exhibited enhanced antioxidant enzyme activities, and showed reduced accumulation of reactive oxygen species compared with wild-type (WT) plants. However, chlorophyll content in GB transgenic plants decreased under both control and salt stress conditions, and sodium ion concentrations were comparable to those in WT plants.
To assess the effects of transgrafting, WT scions were grafted onto codA-expressing rootstocks. Under salt stress conditions, WT scions of the transgrafted plants accumulated GB, exhibited enhanced antioxidant enzyme activities, and showed reduced levels of reactive oxygen species. Although sodium ion accumulation was comparable to that in salt-treated control WT homografts, chlorophyll content was maintained at levels similar to those of the control WT homografts, indicating that the growth-related drawbacks associated with GB accumulation were mitigated.
Transcriptomic profiles of non-GM scions grafted onto codA-transformed rootstocks were clearly distinct from those of control scions in WT homografts. Upregulated genes were enriched in stress-responsive and antioxidant-related pathways, whereas genes associated with photosynthesis and water transport processes tended to be downregulated.
Collectively, these findings demonstrate that transgrafting with codA-expressing rootstocks systemically alters physiological and transcriptional responses, partially conferring salt stress tolerance to non-transgenic scions without inducing GB-associated chlorophyll reduction.
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