The Coordination of Ethylene and Other Hormones in Primary Root Development

Abstract

The primary root is the basic component of root systems, initiates during embryogenesis and develops shortly after germination, and plays a key role in early seedling growth and survival. The phytohormone ethylene shows significant inhibition of the growth of primary roots. Recent findings have revealed that the inhibition of ethylene in primary root elongation is mediated via interactions with phytohormones, such as auxin, abscisic acid, gibberellin, cytokinins, jasmonic acid, and brassinosteroids. Considering that Arabidopsis and rice are the model plants of dicots and monocots, as well as the fact that hormonal crosstalk in primary root growth has been extensively investigated in Arabidopsis and rice, a better understanding of the mechanisms in Arabidopsis and rice will increase potential applications in other species. Therefore, we focus our interest on the emerging studies in the research of ethylene and hormone crosstalk in primary root development in Arabidopsis and rice.

Analysis of the Barley Malt Rootlet Proteome

“…It is interesting to note that the levels of IAA are significantly higher in the kilned seeds when compared to the fresh seeds. There is a plethora of literature demonstrating a vital role for the phytohormones in the root developmental processes [23]. KEGG pathway analysis identified the linolenic acid metabolic pathway that was associated with JA biosynthesis was enriched ( Figure S3).…”

1-Aminocyclopropane 1-Carboxylic Acid and Its Emerging Role as an Ethylene-Independent Growth Regulator

“…There is a complex crosstalk between ethylene and other plant hormones at the level of signaling and/or biosynthesis, the latter of which includes both transcriptional and posttranscriptional regulation of ACS (reviewed in Kazan and Manners, 2012;Muday et al, 2012;Van de Poel et al, 2015;Shigenaga and Argueso, 2016;Hu et al, 2017;Liu et al, 2017;Zemlyanskaya et al, 2018;Bürger and Chory, 2019;Qin et al, 2019). For example, cytokinin and brassinosteroid additively increase the stability of type-2 ACS proteins independently of their TOE domains ).…”

Role of the Cytokinin-Activated Type-B Response Regulators in Hormone Crosstalk

“…Type-B ARR binding sites are found to be associated with genes involved in ethylene biosynthesis and signal transduction ( Figure 2); note that ethylene does not require specific mechanisms for inactivation or transport due to the fact of its gaseous nature and ability to diffuse across cell membranes. Two ACS genes are identified, ACS2 expression being upregulated by cytokinin, consistent with cytokinin-activating ethylene biosynthesis in a type-B ARR-dependent manner [105,106]. Additionally, the type-B ARRs bind to many genes that affect ethylene signal transduction.…”

“…Cytokinin and ethylene often function antagonistically in the shoot, with cytokinin being associated with greening and cell proliferation and ethylene with aging processes such as ripening and senescence and the inhibition of cell proliferation [2,3,101,103,104]. On the other hand, the two hormones operate cooperatively in processes such as the regulation of root growth, where both hormones serve to inhibit root growth through effects on cell proliferation and cell elongation [105][106][107][108][109][110]. Significantly, cytokinin positively stimulates ethylene biosynthesis by activating ACC synthases (ACSs) via both transcriptional and post-transcriptional mechanisms [89,106], the production of ethylene facilitating the ability of cytokinin to inhibit hypocotyl elongation in dark-grown seedling as well as to inhibit root growth [89,[106][107][108][109].…”