Ectopic expression of ARGOS8 reveals a role for ethylene in root‐lodging resistance in maize

Abstract

Ethylene plays a critical role in many diverse processes in plant development. Recent studies have demonstrated that overexpression of the maize ARGOS8 gene reduces the plant's response to ethylene by decreasing ethylene signaling and enhances grain yield in transgenic maize plants. The objective of this study was to determine the effects of ethylene on the development of nodal roots, which are primarily responsible for root-lodging resistance in maize. Exogenous application of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) was found to promote the emergence of nodal roots. Transcriptome analysis of nodal tissues revealed that the expression of genes involved in metabolic processes and cell wall biogenesis was upregulated in response to ACC treatment, supporting the notion that ethylene is a positive regulator for the outgrowth of young root primordia. In BSV::ARGOS8 transgenic plants with reduced ethylene sensitivity due to constitutive overexpression of ARGOS8, nodal root emergence was delayed and the promotional effect of ACC on nodal root emergence decreased. Field tests showed that the BSV::ARGOS8 plants had higher root lodging relative to non-transgenic controls. When ARGOS8 expression was controlled by the developmentally regulated promoter FTM1, which conferred ARGOS8 overexpression in adult plants but not in the nodal roots and nodes in juvenile plants, the FTM1::ARGOS8 plants had no significant difference in root lodging compared with the wild type but produced a higher grain yield. These results suggest that ethylene has a role in promoting nodal root emergence and that a delay in nodal root development has a negative effect on root-lodging resistance in maize.

Maize brace roots provide stalk anchorage

“…The uppermost whorls of brace roots may remain aerial with the lower whorls penetrating into the soil. As their name suggests, the brace roots that penetrate the soil have been proposed to provide anchorage and limit root lodging , Shi et al, 2019, Sharma and Carena, 2016. Previous studies linking brace roots to root lodging-resistance have identified the brace root traits that are correlated with higher lodging-resistance as (a) a higher number of roots in a whorl [Sharma andCarena, 2016, Liu et al, 2012], (b) more overall brace root whorls entering the soil [Sharma andCarena, 2016, Shi et al, 2019], and (c) a higher brace root spread width [Sharma and Carena, 2016].…”

Improving Lodging Resistance: Using Wheat and Rice as Classical Examples

“…Some previous results also witnessed that ethylene signaling in rice not only triggers aerenchyma development in primary roots together with its involvement in the regulation process of constitutive aerenchyma, but also plays a role in root elongation [125]. To enlighten the crucial role of ethylene in the complex lodging mechanism, one example related to study in Zea mays plant where Shi et al [126] investigated the effects of ethylene on the development of nodal roots, which are considered to be responsible for root-lodging resistance. Results revealed that ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) strongly support nodal roots emergence in maize.…”

“…Results revealed that ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) strongly support nodal roots emergence in maize. Further study of the transcriptomic analysis showed that genes expression which is involved in metabolic processes and cell wall biogenesis went up under the treatment application of ACC [126]. This implies the notion that ethylene is positively associated to regulate the outgrowth of young root primordial to ensure root-lodging resistance in maize.…”

Maize brace roots provide stalk anchorage

“…The uppermost whorls of brace roots may remain aerial with the lower whorls penetrating into the soil. As their name suggests, the brace roots that penetrate the soil have been proposed to provide anchorage and limit root lodging (Liu et al, 2012;Sharma & Carena, 2016;Shi et al, 2019). Previous studies linking brace roots to root lodging-resistance have identified the brace root traits that are correlated with higher lodging-resistance as (a) a higher number of roots in a whorl (Liu et al, 2012;Sharma & Carena, 2016), (b) more overall brace root whorls entering the soil (Sharma & Carena, 2016;Shi et al, 2019), and (c) a higher brace root spread width (Sharma & Carena, 2016).…”