Physiological and DNA methylation analysis provides epigenetic insights into kenaf cadmium tolerance heterosis.

Soil heavy metal pollution is one of the most challenging problems. Kenaf is an important natural fiber crop with strong heterosis and a higher tolerance to heavy metals. However, little is known about the molecular mechanisms of kenaf heavy metal tolerance, especially the mechanism of genomic DNA methylation regulating heterosis. In this study, kenaf cultivars CP085, CP089, and their hybrid F 1 seedlings were subjected to 300 µM cadmium stress and found obvious heterosis of cadmium resistance in morphology and antioxidant enzyme activity of F 1 hybrid seedlings. Through methylation-sensitive amplification polymorphism (MSAP) analysis, we highlighted that the total DNA methylation level under cadmium decreased by 16.9 % in F 1 and increased by 14.0 % and 3.0 % in parents CP085 and CP089, respectively. The hypomethylation rate was highest (21.84 %), but hypermethylation was lowest (17.24 %) in F 1 compared to parent cultivars. In particular, principal coordinates analysis (PCoA) indicates a significant epigenetic differentiation between F 1 and its parents under cadmium. Furthermore, 21 differentially methylated DNA fragments (DMFs) were analyzed. Especially, the expression of NPF2.7 , NADP-ME , NAC71 , TPP-D , LRR-RLKs, and DHX51 genes were changed due to cadmium stress and related to cytosine methylation regulation. Finally, the knocked-down of the differentially methylated gene NPF2.7 by virus-induced gene silencing (VIGS) resulted in increased sensitivity of kenaf seedlings under cadmium stress. It is speculated that low DNA methylation levels can regulate gene expression that led to the heterosis of cadmium tolerance in kenaf. • Kenaf hybrid showed significant heterosis to Cd stress and with enhanced Cd transport capacity compared with its parents. • The stronger anti-oxidant ability is positively related to F 1 seedling heterosis under Cd stress. • MSAP revealed the down regulation total DNA methylation increased F 1 Cd tolerance capacity. • The expression of key genes including NPF2.7 , NADP-ME , NAC71 , TPP-D , LRR-RLKs and DHX51 were involved in plant growth and Cd stress response. • VIGS of gene NPF2.7 increased kenaf to Cd tolerance. [ABSTRACT FROM AUTHOR]