The ABSCISIC ACID INSENSITIVE 3 (ABI3) gene is modulated by farnesylation and is involved in auxin signaling and lateral root development in Arabidopsis

Abstract

z Each of these authors contributed equally to this study. SummaryGenetic screens have identi®ed a number of genes that regulate abscisic acid (ABA) responsiveness in Arabidopsis. Using a combination of suppressor screens and double mutant analysis, we have determined a genetic relationship for a number of these ABA response loci. Based on germination in the presence of exogenous ABA, the ABI1 and ABI2 phosphatases act at or upstream of the ERA1 farnesyl transferase and the ABI3 and ABI5 transcription factors act at or downstream of ERA1. In contrast with ABI3 and ABI5, the ABI4 transcription factor appears to act at or upstream of ERA1. Based on reporter gene constructs, the upstream regulation of ABI3 by ERA1 occurs at least partially at the level of transcription, suggesting that this lipid modi®cation is required to attenuate ABI3 expression. Similar experiments also indicate that ABI3 is auxin inducible in lateral root primordia. Related to this, loss-of-function abi3 alleles show reduced lateral root responsiveness in the presence of auxin and an auxin transport inhibitor, and era1 mutants have increased numbers of lateral roots. These results suggest the possibility that genes identi®ed through ABA responsive germination screens such as ERA1 and ABI3 have functions in auxin action in Arabidopsis.

Interactions between theS-Domain Receptor Kinases and AtPUB-ARM E3 Ubiquitin Ligases Suggest a Conserved Signaling Pathway in Arabidopsis

“…Our epistatic analysis places the role of AtPUB9 during ABA responses upstream or at the same level of the transcription factor, ABI3, whereas our crosses of ARK1-deficient lines with abi3-6 failed to isolate any double homozygotes, indicating a genetic interaction between these two loci. ABI3 has been previously shown to play a role in ABA responses at or downstream of the ERA1 farnesyl transferase, whereas the ABI1 and ABI2 protein phosphatases act at or upstream of ERA1 (Brady et al, 2003). Our research presented here suggests that AtPUB9 is yet another E3 ligase regulating some aspect of ABA responses, specifically during germination, and AtPUB9 itself may be activated by the ARK1 receptor kinase in this role.…”

DEXH Box RNA Helicase–Mediated Mitochondrial Reactive Oxygen Species Production in Arabidopsis Mediates Crosstalk between Abscisic Acid and Auxin Signaling

“…a modified IAA pattern (Tsukagoshi et al, 2010); the transgenic plants exhibited enhanced ABA sensitivity, which was further enhanced by adding IBA, IBA-Glc, or IAA. Auxin can also enhance ABA inhibition of seed germination (Brady et al, 2003;Liu et al, 2007). Mutations in INDOLE-3-BUTYRIC ACID RE-SPONSE5 dual specificity phosphatase and RCN1 protein phosphatase 2A lead to auxin insensitivity but also to ABA insensitivity in germination and root growth.…”

Protein Geranylgeranyltransferase I Is Involved in Specific Aspects of Abscisic Acid and Auxin Signaling in Arabidopsis

“…Because ABA and auxin signaling are related and both are modulated by protein farnesylation (Brady et al, 2003), the auxin responsiveness of wild-type and ggb seedlings was examined. As shown in Figure 9, stimulation of lateral root formation in response to .…”

“…era1 is epistatic to abi1 and abi2, suggesting that ERA1 acts at or downstream of the ABI1 and ABI2 phosphatases. However, ERA1 acts at or upstream of the ABI3 and ABI5 transcription factors, and transcription of the ABI3 gene has been shown to be elevated in era1 plants (Brady et al, 2003). In addition to an enhanced response to ABA, era1 mutants also exhibit enlarged meristems and supernumerary floral organs (Running et al, 1998;Bonetta et al, 2000;Yalovsky et al, 2000;Ziegelhoffer et al, 2000).…”