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

Abstract

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.

Regulation of Root Traits for Internal Aeration and Tolerance to Soil Waterlogging-Flooding Stress

“…This finding suggests that ethylene is involved not only in inducible aerenchyma formation but also in constitutive aerenchyma formation. This evidence was confirmed by Yamauchi et al (2016), who found that 1-MCP also partially suppressed aerenchyma formation in rice roots in aerated nutrient solution. The formation of some aerenchyma even when roots were treated with 1-MCP (Yukiyoshi and Karahara, 2014;Yamauchi et al, 2016) could indicate that constitutive aerenchyma formation in rice roots is regulated by an ethyleneindependent pathway, as well as the ethylenedependent pathway, if the 1-MCP treatment blocked all perception of ethylene.…”

“…However, a greater amount of aerenchyma also would facilitate some venting of this ethylene from the roots (Visser and Pierik, 2007); such venting would only impact aerenchyma formation if ethylene then remained below the threshold concentration required, but this seems unlikely. Exogenously supplied ACC increased ethylene production and aerenchyma formation in rice roots under aerobic conditions (Yamauchi et al, , 2016), demonstrating that a low level of ACC production is likely rate limiting for ethylene biosynthesis in these aerobic roots. On the other hand, the levels of ethylene production in roots of rice and maize reflected the levels of ACO expression; a higher ACO expression level in rice roots than in maize roots under aerated conditions was associated with a more pronounced increase of ethylene production in rice roots than in maize roots immediately after the onset of low-oxygen conditions (Yamauchi et al, 2016).…”

Stress responses of native and exotic grasses in a Neotropical savanna predict impacts of global change on invasion spread

“…), which may promote grass survival under hypoxia (Yamauchi et al . ), and were also found in other African grasses (Baruch ). Although these responses supported the broader distribution of these exotic species in comparison with U. decumbens , these two species were more affected by soil waterlogging than the two most widespread native grasses at our study sites ( L. chrysothrix and T. spicatus ).…”

Sorghum stem aerenchyma formation is regulated by SbNAC_D during internode development

“…In species such as rice, some root aerenchyma form in the absence of flooding and additional aerenchyma form in response to flooding or ethylene treatment (Yamauchi, Shimamura, Nakazono, & Mochizuki, 2013). In maize, accumulation of aerenchyma is induced by hypoxia (Drew et al, 2000;Yamauchi et al, 2016). In contrast, the wetland species Juncus effusus form root aerenchyma in the absence of ethylene and flooding (Visser & Bogemann, 2006).…”