Auxin: Hormonal Signal Required for Seed Development and Dormancy

Abstract

The production of viable seeds is a key event in the life cycle of higher plants. Historically, abscisic acid (ABA) and gibberellin (GAs) were considered the main hormones that regulate seed formation. However, auxin has recently emerged as an essential player that modulates, in conjunction with ABA, different cellular processes involved in seed development as well as the induction, regulation and maintenance of primary dormancy (PD). This review examines and discusses the key role of auxin as a signaling molecule that coordinates seed life. The cellular machinery involved in the synthesis and transport of auxin, as well as their cellular and tissue compartmentalization, is crucial for the development of the endosperm and seed-coat. Thus, auxin is an essential compound involved in integuments development, and its transport from endosperm is regulated by AGAMOUS-LIKE62 (AGL62) whose transcript is specifically expressed in the endosperm. In addition, recent biochemical and genetic evidence supports the involvement of auxins in PD. In this process, the participation of the transcriptional regulator ABA INSENSITIVE3 (ABI3) is critical, revealing a cross-talk between auxin and ABA signaling. Future experimental aimed at advancing knowledge of the role of auxins in seed development and PD are also discussed.

Endogenous indole-3-acetamide levels contribute to the crosstalk between auxin and abscisic acid, and trigger plant stress responses in Arabidopsis

“…ABA and gibberellins are essential determinants of seed development and dormancy ( Carrera-Castaño et al , 2020 ). A recent publication also highlighted a direct role of auxin in seed dormancy ( Matilla, 2020 ). In addition, crosstalk between IAA and ABA in seed development and germination has been reported to occur on both the transcriptional and the metabolic level ( Chauffour et al , 2019 ; He et al , 2020 ).…”

Beyond the Usual Suspects: Physiological Roles of the Arabidopsis Amidase Signature (AS) Superfamily Members in Plant Growth Processes and Stress Responses

“…In this context, the IAM connection with gibberellin signaling through the recently reported repression of GNC and CGA1 transcription factors, both DELLAs downstream effectors is particularly noteworthy [71]. Furthermore, the recently reported direct role of auxin in seed dormancy [89], as well as the transcriptional and metabolic crosstalk between IAA and ABA in seed development and germination [90,91], have led to propose an additional crosstalk connecting AMI1/IAM contents and ABA-related processes, with prosperous seedling development and germination. As demonstrated by the Arabidopsis germination rate reduction in response to IAM application, deficient AMI1 activity most probably enhances ABA production, and later results in aberrant embryo and seed size [61].…”

Seed Dormancy: Molecular Control of Its Induction and Alleviation

“…Thus, it was demonstrated, for the first time at the molecular level, a role for auxin in PD through stimulation of ABA signaling, identifying auxin as a dormancy promotor [ 24 ]. Matilla (2020) [ 25 ] carries out here an in-depth review of the participation of auxin in embryogenesis, PD, and germination. The dynamic of expression and localization (i.e., proembryo, hypophysis, and suspensor) of several key genes for the biosynthesis and transport of auxins in the globular phase was carefully checked (Figure 1 of the review).…”