Resilience of Ricinus communis L. to high temperatures during germination and seedling growth resulting from efficient superoxide dismutase modulation

Abstract

Ricinus communis L., known as castor, is an oilseed crop species with increasing bioindustrial demand for its high-value oil, mainly cultivated by smallholder farming systems under abiotic stresses in semiarid areas. Abiotic stresses lead to increased reactive oxygen species production, inducing oxidative stress that damages cells and impacts seed germination and seedling establishment. Plants response to abiotic stresses involve the superoxide dismutase enzyme (SOD) that act catalyzing superoxide radical (O₂⁻) into hydrogen peroxide (H₂O₂). The characterization of RcSOD genes under heat stress and different compartments can offer valuable insights into identifying the responsive RcSOD genes. Cis-element and miRNA predictions were employed for RcSOD genes. The qPCR analysis of RcSOD gene expression was conducted during germination and early seedling stages at three distinct temperatures and also in roots, leaves, and cotyledons. Subcellular localization was performed in Nicotiana benthamiana Domin leaves. RcSOD has responsive elements in the promoter region related to abiotic stresses, and there is a possible regulation of RcCuZnSOD3 and RcCCuSOD4 by Rcmi-RNA398a-b. The RcCuZnSOD1 and RcFeSOD8 genes were upregulated by heat stress during initial germination, while RcCuZnSOD3, RcCCuSOD4, and RcFeSOD7 were upregulated during radicle protrusion and early seedling stages. Besides, the CuZnSOD and RcFeSOD8 genes were upregulated by heat stress in seedling roots. Additionally, we show the modulation of RcSOD genes in cotyledons and leaves in different stages and subcellular localization in N. benthamiana. Our results contribute to understanding RcSOD family and their potential as markers for genetic engineering or molecular-assisted breeding aimed at higher tolerance to abiotic stresses.