Abstract
Abscisic acid (ABA) transporters are essential for the transport of ABA from its sites of synthesis to its multiple sites of action within plants and are key players in plant stress responses. Despite their importance, there is limited information on ABA transporters in crop plants. In this study, we isolated and characterized an ABA transporter-like 1 (AhATL1) gene from peanut (Arachis hypogaea L.) whose cognate protein, AhATL1, is a member of the ATP-binding cassette transporter G subfamily and localizes to the plasma membrane. The expression of both the AhATL1 transcript and the corresponding protein were upregulated by water stress and treatment with exogenous ABA. Overexpression of AhATL1 in ecotype Columbia (Col) Arabidopsis (AhATL1-OX) plants reduced ABA sensitivity. When AhATL1-OX and Arabidopsis Col plants were subjected to dehydration stress, the expression of 9-cis-epoxycarotenoid dioxygenase 3 (AtNCED3) and responsive to desiccation 29 A (AtRD29A) accumulated rapidly in rosette leaves of both lines. In contrast, while expression of ATP-binding cassette G 40 (AtABCG40) was increased in Col rosette leaves, there was no change in expression of AtABCG40 in AhATL1-OX leaves. Similarly, water loss from detached leaves of AhATL1-OX plants was more rapid than from Col leaves. Therefore, we suggest that the function of AhATL1 is probably to modulate ABA sensitivity by specifically influencing ABA import into cells.
Highlights
Abscisic acid (ABA) is a key phytohormone involved in a host of biological processes, including embryo and seed maturation, postgerminative growth, and abiotic stress responses (Tuteja, 2007)
The prevailing view has been that, when a plant experiences water stress, the ABA concentration increases in the root due to a local increase in its biosynthesis, and ABA moves via phloem transport from the roots to the leaves, where it regulates stomatal aperture (Nambara and Marion-Poll, 2005; Rodrigues et al, 2009)
Four ABA transporters have been identified in Arabidopsis; these have various transport functions depending on physiological state and tissue (Kang et al, 2010, 2015; Kuromori et al, 2010; Kanno et al, 2012)
Summary
Abscisic acid (ABA) is a key phytohormone involved in a host of biological processes, including embryo and seed maturation, postgerminative growth, and abiotic stress responses (Tuteja, 2007). When higher plants are exposed to drought, the levels of endogenous ABA increase and downstream signaling pathways are activated (Hwang et al, 2016). AhATL1 Gene Reduces ABA Sensitivity by turnover or conjugation, and levels are further modified by compartmentation and transport (Nambara and Marion-Poll, 2005; Finkelstein, 2013). The translocation of ABA between cells, tissues and organs plays an important role in the physiological response of plants to stress conditions. ABA is rapidly synthesized in root vascular parenchyma under root stress, and is rapidly transported to leaf tissues, where it induces stomatal closure in peanut and Arabidopsis (Boursiac et al, 2013; Puértolas et al, 2015; Hu et al, 2016)
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