Ethylene is involved in the complete-submergence induced increase in root iron and manganese plaques in Oryza sativa

Abstract

Flooding is one of the most important abiotic constraints on rice yields in rain-fed lowlands. During the submergence period, ethylene accumulates rapidly to a physiologically active level in the tissues of submerged plants. Also, iron and manganese plaque formation on roots is an adaptation that allows rice-like plant species to survive in their natural aquatic habitats. This study provides evidence of a time-dependent increase in the iron and manganese plaque content of rice root surfaces during 96 h of complete submergence (CS), accompanied by the increased expression in roots of genes in the OsACS (OsACS1, OsACS2, OsACS4 and OsACS5) and OsACO (OsACO1, OsACO2, OsACO3 and OsACO7) families. To further investigate ethylene action in root plaque formation, rice seedlings were completely submerged in Kimura B nutrient solutions containing different concentrations of Fe2+ or Mn2+. Under these conditions, root plaques were induced dramatically in an almost dose-dependent manner. Iron and manganese plaque formation was promoted by the ethylene precursor 1-aminocyclopropane-1-carboxylic acid and blocked by the ethylene biosynthesis inhibitor aminoethoxyvinyl glycine (AVG) in seedlings grown on media supplemented or not with Fe2+ or Mn2+. Furthermore, submergence-induced iron and manganese root plaque formation was decreased by pretreatment with 5 μM AVG for 12 h. Our findings suggest that ethylene signaling is involved in CS-induced iron and manganese root plaque formation in rice.