Multifaceted Signaling Networks Mediated by Abscisic Acid Insensitive 4

Abstract

Although ABSCISIC ACID INSENSITIVE 4 (ABI4) was initially demonstrated as a key positive regulator in the phytohormone abscisic acid (ABA) signaling cascade, multiple studies have now shown that it is actually involved in the regulation of several other cascades, including diverse phytohormone biogenesis and signaling pathways, various developmental processes (such as seed dormancy and germination, seedling establishment, and root development), disease resistance and lipid metabolism. Consistent with its versatile biological functions, ABI4 either activates or represses transcription of its target genes. The upstream regulators of ABI4 at both the transcription and post-transcription levels have also been documented in recent years. Consequently, a complicated network consisting of the direct target genes and upstream regulators of ABI4, through which ABI4 participates in several phytohormone crosstalk networks, has been generated. In this review, we summarize current understanding of the sophisticated ABI4-mediated molecular networks, mainly focusing on diverse phytohormone (including ABA, gibberellin, cytokinin, ethylene, auxin, and jasmonic acid) crosstalks. We also discuss the potential mechanisms through which ABI4 receives the ABA signal, focusing on protein phosphorylation modification events.

The ABI4‐RbohD/VTC2 regulatory module promotes reactive oxygen species (ROS) accumulation to decrease seed germination under salinity stress

“…ABI4, which was initially demonstrated to be a key positive regulator in the ABA signaling transduction pathway (Finkelstein et al ., 1998; Soderman et al ., 2000), has been shown to act as a versatile transcription factor involved in diverse crosstalk networks with other phytohormones, plant development periods and also in abiotic/biotic stress responses (Kong et al ., 2013; Shu et al ., 2013, 2016a,b, 2018; Wind et al ., 2013; Li et al ., 2014; Lee et al ., 2015; Dong et al ., 2016; Guo et al ., 2016; Xie et al ., 2016; Xu et al ., 2016; Huang et al ., 2017; Cheng et al ., 2018; Yan et al ., 2019; Chandrasekaran et al ., 2020). It should be noted that an early study showed that ABI4 is essential for ascorbic acid (AsA)‐mediated plant growth and jasmonate‐dependent defense signaling (Kerchev et al ., 2011).…”

Plant-Specific AtS40.4 Acts as a Negative Regulator in Abscisic Acid Signaling During Seed Germination and Seedling Growth in Arabidopsis

“…Abscisic acid (ABA) is a key phytohormone, which plays versatile functions in developmental regulation and various environmental stress response. The ABA plays roles in spatiotemporal and dose-dependent ways, which is connected with its diverse functions ( Liu et al, 2019 ; Lu et al, 2019 ; Chandrasekaran et al, 2020 ; Xie et al, 2020 ). ABA is well-known for its stress-related properties, but it also has been proven to regulate plant growth and development such as seed germination, root growth and flowering transition ( Huang et al, 2017 ; Belda-Palazon et al, 2018 ; Xiong et al, 2019 ).…”

“…A subset of key genes involved in ABA signaling has been identified. Among these genes, ABA INSENTIVE ( ABI ) 1 , ABI2 , ABI3 , ABI4 , and ABI5 , encode five key negative or active regulators of ABA response ( Leung et al, 1997 ; Skubacz et al, 2016 ; Chandrasekaran et al, 2020 ). ABI1 and ABI2 encode type 2C protein phosphatases (PP2Cs) that play roles as negative regulators of ABA signaling.…”

“…PP2Cs interact with and inactivate ABA-activated sucrose non-fermenting 1-related protein kinase 2 (SnRK2) members, a core kinase in ABA signaling ( Leung et al, 1997 ). ABI3, ABI4, and ABI5 are transcription factors (TFs) of the B3, APETALA2, and basic leucine zipper families, respectively, and share overlapping functions in ABA signaling as positive regulators ( Finkelstein et al, 2002 ; Cheng et al, 2014 ; Liu et al, 2017 ; Chandrasekaran et al, 2020 ).…”

“…ABREs are major cis-acting regulators in ABA-dependent gene expression ( Kim et al, 2004 ; Wang et al, 2019 ; Chen et al, 2020 ). ABI3, ABI4, and ABI5 bind directly to the ABREs of the promoter regions of a subset of genes, thereby controlling their transcription levels ( Carles et al, 2002 ; Ezcurra et al, 2000 ; Mizoi et al, 2012 ; Shu et al, 2013 ; Skubacz et al, 2016 ; Wang et al, 2019 ; Chandrasekaran et al, 2020 ; Collin et al, 2020 ). Notably, ABI3, ABI4, and ABI5 either activate or repress gene expression in diverse processes depending on DNA binding.…”