Lack of sufficient water is a major limiting factor to crop production worldwide, and the development of drought-tolerant germplasm is needed to improve crop productivity. The phytohormone ethylene modulates plant growth and development as well as plant response to abiotic stress. Recent research has shown that modifying ethylene biosynthesis and signaling can enhance plant drought tolerance. Here, we report novel negative regulators of ethylene signal transduction in Arabidopsis (Arabidopsis thaliana) and maize (Zea mays). These regulators are encoded by the ARGOS gene family. In Arabidopsis, overexpression of maize ARGOS1 (ZmARGOS1), ZmARGOS8, Arabidopsis ARGOS homolog ORGAN SIZE RELATED1 (AtOSR1), and AtOSR2 reduced plant sensitivity to ethylene, leading to enhanced drought tolerance. RNA profiling and genetic analysis suggested that the ZmARGOS1 transgene acts between an ethylene receptor and CONSTITUTIVE TRIPLE RESPONSE1 in the ethylene signaling pathway, affecting ethylene perception or the early stages of ethylene signaling. Overexpressed ZmARGOS1 is localized to the endoplasmic reticulum and Golgi membrane, where the ethylene receptors and the ethylene signaling protein ETHYLENE-INSENSITIVE2 and REVERSION-TO-ETHYLENE SENSITIVITY1 reside. In transgenic maize plants, overexpression of ARGOS genes also reduces ethylene sensitivity. Moreover, field testing showed that UBIQUITIN1:ZmARGOS8 maize events had a greater grain yield than nontransgenic controls under both drought stress and well-watered conditions.There is an increasing demand for food and feed due to global population growth, urbanization, and rapid middle-class emergence. Lack of water limits crop yields worldwide; Bot et al. (2000) estimated that 45% of agricultural lands are subject to continuous or frequent drought conditions. Drought-tolerant varieties can reduce the impact of drought on crop productivity. The phytohormone ethylene regulates many aspects of plant growth and development, from seed germination, leaf expansion, and floral transition to organ senescence, fruit ripening, and the response to abiotic stresses, such as drought, high temperature, freezing, shading, and nutrient deficiency. Ethylene is one of the most widely used hormones in agriculture to increase yield and reduce production costs. For example, ethylene can reduce lodging in wheat (Triticum aestivum) and barley (Hordeum vulgare) by shortening the stem, therefore improving grain yield and quality. Studies have shown that inhibitors of ethylene biosynthesis and perception can mitigate yield loss by enhancing plant tolerance to abiotic stresses, such as drought, heat, and a combination of both (Hays et al., 2007;Kawakami et al., 2010Kawakami et al., , 2013Huberman et al., 2014). This study explores the potential to improve crop performance by modifying ethylene sensitivity.At the molecular level, ethylene responses in Arabidopsis (Arabidopsis thaliana) are initiated by the binding of ethylene to a family of endoplasmic reticulum (ER)-and Golgi membrane-localized receptors...

Increasing maize grain yield has been a major focus of both plant breeding and genetic engineering to meet the global demand for food, feed, and industrial uses. We report that increasing and extending expression of a maize MADS-box transcription factor gene, zmm28, under the control of a moderate-constitutive maize promoter, results in maize plants with increased plant growth, photosynthesis capacity, and nitrogen utilization. Molecular and biochemical characterization of zmm28 transgenic plants demonstrated that their enhanced agronomic traits are associated with elevated plant carbon assimilation, nitrogen utilization, and plant growth. Overall, these positive attributes are associated with a significant increase in grain yield relative to wild-type controls that is consistent across years, environments, and elite germplasm backgrounds.

A single transgene ARGOS1 positively impacts yield of field-grown hybrid maize. Two predominant alleles from elite hybrid breeding germplasm differed in transgene efficacy, but both alleles combined in a transgenic stack outperformed each alone, consistent with a single-locus heterotic effect

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.

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