The role of Arabidopsis thaliana RASD1 gene in ABA-dependent
abiotic stress response
, D. Milioni
, M. Martzikou
& K. Haralampidis
1 Faculty of Biology, Department of Botany, National and Kapodistrian University of Athens, Athens,Greece
2 Department of Agricultural Biotechnology, Agricultural University of Athens, Athens, Greece
Abiotic stress; abscisic acid; Arabidopsis;
C2-domain protein; dehydration; salinity;
K. Haralampidis, Biology Department, Division
of Botany, Molecular Plant Development
Laboratory, National and Kapodistrian
University of Athens, 15701 Athens, Greece.
Received: 13 October 2017; Accepted: 6
Abiotic stress is one of the key parameters affecting plant productivity. Drought and
soil salinity, in particular, challenge plants to activate various response mechanisms to
withstand these adverse growth conditions. While the molecular events that take place
are complex and to a large extent unclear, the plant hormone abscisic acid (ABA) is
considered a major player in mediating the adaptation of plants to stress.
Here we report the identiﬁcation of an ABA-insensitive mutant from Arabidopsis
thaliana. A combination of molecular, genetic and physiology approaches were imple-
mented, to characterise the AtRASD1 locus (
RESPONSIVENESS TO ABA SALT AND
DROUGHT 1) and to investigate its role in plant development.
RASD1 is expressed predominantly in the vascular system of A. thaliana and encodes a
peptide of unknown function with no similarity to any known sequence to date. The
protein is localised in the nucleus and the cytoplasm, and RASD1-impaired plants are
drought-intolerant and insensitive to exogenous ABA and NaCl during germination
and root growth.
Our data indicate that RASD1 is involved in ABA-dependent signal transduction path-
ways and therefore in enabling plants to activate response mechanisms related to seed
germination and abiotic stress.
The ﬂowering plant Arabidopsis thaliana is considered an
important model plant for studies of plant gene functions due
its small genome and short life cycle. Although the whole-gen-
ome sequence of Arabidopsis was completed in 2000 (The Ara-
bidopsis Genome Initiative) and related information is publicly
available, the functions of approximately one third of its genes
remain unclear. Despite existing comprehensive experimental
and computational studies, many Arabidopsis genes remain
uncharacterised in terms of biological roles and are annotated
in the databases to encode putative proteins or proteins of
unknown function (Kourmpetis et al. 2011; Lee et al. 2015). In
order to improve functional annotation, a number of
approaches have been used, which utilise information obtained
from transcriptomic and metabolic proﬁles among plant tis-
sues (Sakurai et al. 2013), Arabidopsis transcriptomics (Lan
et al. 2007; Obayashi et al. 2014), Arabidopsis mutant line phe-
notypes (Akiyama et al. 2014; Myouga et al. 2013), computa-
tional-derived protein–protein interaction data (Kourmpetis
et al. 2011), proteomic data to predict secondary structures
and functions (Kurotani et al. 2014) and using probabilistic
functional gene networks (Hwang et al. 2011; Lee et al. 2015).
Despite the increased functional annotations by these methods,
experimental evidence is still needed to safely assign a function
to each predicted gene or gene product.
Since plants are sessile organisms, scientist have tried for
decades to identify and characterise novel gene loci associated
with stress adaptations to generate plants tolerant to various
environmental conditions. Among the important traits that are
targeted are improved resistance to biotic and abiotic stresses,
such as pathogens, salinity, heat and drought (Imam et al.
2016). Abiotic stresses, in particular, are dominant factors
affecting not only crop yield but also food quality and food
safety (Halford et al. 2014). Drought and salt act through
unique and overlapping stress signalling pathways, in which
the phytohormone abscisic acid (ABA) plays an important role
(Jiang & Hartung 2008; Sah et al. 2016; Zhu 2016). Our under-
standing of the ABA signal transduction pathway improved
dramatically with characterisation of the ABA receptors and
their mechanisms of action (Ma et al. 2009; Melcher et al.
2009; Miyazono et al. 2009; Park et al. 2009). It has been shown
that ABA elicits plant responses through the PYR/PYL/RCAR
receptors (Rodriguez et al. 2014; Diaz et al. 2016; Sun et al.
2016). ABA perception inhibits type 2C protein phosphatases
(PP2Cs), which in turn activates accumulation of SNF1-
RELATED PROTEIN KINASES (SnRK2s). This signalling
pathway stimulates the induction of a number of transcription
factors and the expression of ABA-responsive genes and pro-
cesses (Ma et al. 2009; Gonzalez-Guzman et al. 2012; Golldack
2014). On the other hand, intercellular transport of ABA
is mediated through several membrane-type ABC transporters
(Boursiac et al. 2013). Recently, four AtABCG proteins have
been characterised that act as ABA transporters in seeds.
AtABCG25 and AtABCG31 export ABA from the endosperm
to the embryo, whereas AtABCG30 and AtABCG40 transport
Plant Biology 20 (2018) 307–317 © 2017 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands
Plant Biology ISSN 1435-8603