The Arabidopsis Vacuolar Sorting Receptor1 Is Required for Osmotic Stress-Induced Abscisic Acid Biosynthesis  

Abstract

Osmotic stress activates the biosynthesis of the phytohormone abscisic acid (ABA) through a pathway that is rate limited by the carotenoid cleavage enzyme 9-cis-epoxycarotenoid dioxygenase (NCED). To understand the signal transduction mechanism underlying the activation of ABA biosynthesis, we performed a forward genetic screen to isolate mutants defective in osmotic stress regulation of the NCED3 gene. Here, we identified the Arabidopsis (Arabidopsis thaliana) Vacuolar Sorting Receptor1 (VSR1) as a unique regulator of ABA biosynthesis. The vsr1 mutant not only shows increased sensitivity to osmotic stress, but also is defective in the feedback regulation of ABA biosynthesis by ABA. Further analysis revealed that vacuolar trafficking mediated by VSR1 is required for osmotic stress-responsive ABA biosynthesis and osmotic stress tolerance. Moreover, under osmotic stress conditions, the membrane potential, calcium flux, and vacuolar pH changes in the vsr1 mutant differ from those in the wild type. Given that manipulation of the intracellular pH is sufficient to modulate the expression of ABA biosynthesis genes, including NCED3, and ABA accumulation, we propose that intracellular pH changes caused by osmotic stress may play a signaling role in regulating ABA biosynthesis and that this regulation is dependent on functional VSR1.

MYB30 transcription factor regulates oxidative and heat stress responses through ANNEXIN‐mediated cytosolic calcium signaling in Arabidopsis

“…d). We also studied H 2 O 2 ‐induced [Ca 2+ ] cyt elevation in 1128 using the fluorescent dye Fluo‐4 acetoxymethyl (AM) ester, which specifically detects cytosolic free calcium (Wang et al ., 2015b). Before H 2 O 2 treatment, no significant difference was observed in [Ca 2+ ] cyt in roots between wild‐type and 1128 (Fig.…”

De novo Sequencing and Comparative Transcriptomics of Floral Development of the Distylous Species Lithospermum multiflorum

“…The two morphs may have different genes expressed in response to stress or one morph may have a stronger response to stress than the other. Some of the DE genes involved in stress response are influenced by hormones known to be involved in this type of process, including ethylene and abscisic acid, and these genes include various ethylene-responsive transcription factors, abscisic acid receptor pyr1-like, and others (Thirugnanasambantham et al, 2015; Wang et al, 2015) (Table 7). Future research can investigate variation in hormones or hormone response between morphs, which may influence the observed morph-specific responses to stress.…”

Involvement of aerial organs on the ABA accumulation in roots of Citrus plants under water deficit

“…The contribution of each of these substrates to the ABA accumulation remains to be elucidated, but the relative importance of 9-cis-neoxanthin and 9-cis-violanxanthin in ABA biosynthesis could be tissue-specific . Nevertheless, NCED activity is considered the main bottleneck step in the ABA synthesis (Nambara and Marion-Poll, 2005) and, probably for this reason, several NCED genes are present in different species: five in Arabidopsis (Wang et al, 2015;Zhang et al, 2015) and two in citrus Agustí et al, 2007). However, only some of them are strongly linked to ABA accumulation (Wang et al, 2015) whereas the others seem to play an secondary role .…”

“…Nevertheless, NCED activity is considered the main bottleneck step in the ABA synthesis (Nambara and Marion-Poll, 2005) and, probably for this reason, several NCED genes are present in different species: five in Arabidopsis (Wang et al, 2015;Zhang et al, 2015) and two in citrus Agustí et al, 2007). However, only some of them are strongly linked to ABA accumulation (Wang et al, 2015) whereas the others seem to play an secondary role . Xanthoxin is then extruded to the cytosol and oxidized into abscisic aldehyde by a short-chain alcohol dehydrogenase (Xanthoxin dehydrogenase, XantDH; González-Guzmán et al, 2002) which is then converted into ABA by the ABA aldehyde oxidase3 (AAO3), using a molybdenum cofactor activated by the molybdenum cofactor sulfurase (ABA3; Nambara and Marion-Poll, 2005).…”

“…1) where β-carotene is converted through several enzymatic steps into the β,β-xanthophylls, 9-cis-neoxanthin and 9-cisviolaxanthin (9-cis-epoxycarotenoids, Nambara and Marion-Poll 2005). The enzyme 9-cis-epoxycarotenoid dioxygenase (NCED) catalyzes the conversion of both 9-cisneoxanthin or 9-cis-violaxanthin into xanthoxin, in the rate limiting step of ABA biosynthesis (Wang et al 2015). Xanthoxin is then extruded to the cytosol where the final steps of ABA biosynthesis take place Marion-Poll 2005, Thompson et al 2007).…”