Comparative metabolite profiling of salt sensitive Oryza sativa and the halophytic wild rice Oryza coarctata under salt stress.

To better understand the salt tolerance of the wild rice, Oryza coarctata , root tissue-specific untargeted comparative metabolomic profiling was performed against the salt-sensitive Oryza sativa . Under control, O. coarctata exhibited abundant levels of most metabolites, while salt caused their downregulation in contrast to metabolites in O. sativa . Under control conditions, itaconate, vanillic acid, threonic acid, eicosanoids, and a group of xanthin compounds were comparatively abundant in O. coarctata . Similarly, eight amino acids showed constitutive abundance in O. coarctata . In contrast, under control, glycerolipid abundances were lower in O. coarctata and salt stress further reduced their abundance. Most phospholipids also showed a distribution similar to the glycerolipids. Fatty acyls were however significantly induced in O. coarctata but organic acids were prominently induced in O. sativa . Changes in metabolite levels suggest that there was upregulation of the arachidonic acid metabolism in O. coarctata . In addition, the phenylpropanoid biosynthesis as well as cutin, suberin, and wax biosynthesis were also more enriched in O. coarctata , likely contributing to its anatomical traits responsible for salt tolerance. The comparative variation in the number of metabolites like gelsemine, allantoin, benzyl alcohol, specific phospholipids, and glycerolipids may play a role in maintaining the superior growth of O. coarctata in salt. Collectively, our results offer a comprehensive analysis of the metabolite profile in the roots of salt-tolerant O. coarctata and salt-sensitive O. sativa , which confirm potential targets for metabolic engineering to improve salt tolerance and resilience in commercial rice genotypes.