Ethylene‐dependent aerenchyma formation in adventitious roots is regulated differently in rice and maize

• Published in: Plant, cell and environment Vol. 39; no. 10; pp. 2145 - 2157
• Main Authors: Yamauchi, Takaki, Tanaka, Akihiro, Mori, Hitoshi, Takamure, Itsuro, Kato, Kiyoaki, Nakazono, Mikio
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01-10-2016
• Subjects: 1‐aminocyclopropane‐1‐carboxylic acid (ACC); constitutive aerenchyma formation; Cyclopropanes - pharmacology; ethylene; Ethylenes - metabolism; inducible aerenchyma formation; maize (Zea mays); Oryza - anatomy & histology; Oryza - metabolism; Oryza - physiology; Oryza sativa; Oxygen - metabolism; Phylogeny; Plant Growth Regulators - metabolism; Plant Growth Regulators - physiology; Plant Roots - anatomy & histology; Plant Roots - metabolism; Plant Roots - physiology; rice (Oryza sativa); Species Specificity; Zea mays; Zea mays - anatomy & histology; Zea mays - metabolism; Zea mays - physiology; maize (Zea mays); rice (Oryza sativa); constitutive aerenchyma formation; ethylene; 1-aminocyclopropane-1-carboxylic acid (ACC); inducible aerenchyma formation
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.12766

In roots of gramineous plants, lysigenous aerenchyma is created by the death and lysis of cortical cells. Rice (Oryza sativa) constitutively forms aerenchyma under aerobic conditions, and its formation is further induced under oxygen‐deficient conditions. However, maize (Zea mays) develops aerenchyma only under oxygen‐deficient conditions. Ethylene is involved in lysigenous aerenchyma formation. Here, we investigated how ethylene‐dependent aerenchyma formation is differently regulated between rice and maize. For this purpose, in rice, we used the reduced culm number1 (rcn1) mutant, in which ethylene biosynthesis is suppressed. Ethylene is converted from 1‐aminocyclopropane‐1‐carboxylic acid (ACC) by the action of ACC oxidase (ACO). We found that OsACO5 was highly expressed in the wild type, but not in rcn1, under aerobic conditions, suggesting that OsACO5 contributes to aerenchyma formation in aerated rice roots. By contrast, the ACO genes in maize roots were weakly expressed under aerobic conditions, and thus ACC treatment did not effectively induce ethylene production or aerenchyma formation, unlike in rice. Aerenchyma formation in rice roots after the initiation of oxygen‐deficient conditions was faster and greater than that in maize. These results suggest that the difference in aerenchyma formation in rice and maize is due to their different mechanisms for regulating ethylene biosynthesis.
Internal transport of oxygen from shoots to roots through aerenchyma is essential for the survival of plants under oxygen‐deficient conditions in waterlogged soil. A gene encoding 1‐aminocyclopropane‐1‐carboxylic acid oxidase (ACO) is expressed more strongly in rice roots than in maize roots under aerobic conditions. This results in faster and greater stimulation of ethylene production and ethylene‐dependent lysigenous aerenchyma formation in rice roots than in maize roots after the initiation of oxygen‐deficient conditions and explains rice's greater tolerance of waterlogging.