Unravelling molecular responses to moderate dehydration in harvested fruit of sweet orange (Citrus sinensis L. Osbeck) using a fruit-specific ABA-deficient mutant

Abstract

Water stress affects many agronomic traits that may be regulated by the phytohormone abscisic acid (ABA). Within these traits, loss of fruit quality becomes important in many citrus cultivars that develop peel damage in response to dehydration. To study peel dehydration transcriptional responsiveness in harvested citrus fruit and the putative role of ABA in this process, this study performed a comparative large-scale transcriptional analysis of water-stressed fruits of the wild-type Navelate orange (Citrus sinesis L. Osbeck) and its spontaneous ABA-deficient mutant Pinalate, which is more prone to dehydration and to developing peel damage. Major changes in gene expression occurring in the wild-type line were impaired in the mutant fruit. Gene ontology analysis revealed the ability of Navelate fruits to induce the response to water deprivation and di-, tri-valent inorganic cation transport biological processes, as well as repression of the carbohydrate biosynthesis process in the mutant. Exogenous ABA triggered relevant transcriptional changes and repressed the protein ubiquitination process, although it could not fully rescue the physiological behaviour of the mutant. Overall, the results indicated that dehydration responsiveness requires ABA-dependent and -independent signals, and highlight that the ability of citrus fruits to trigger molecular responses against dehydration is an important factor in reducing their susceptibility to developing peel damage.

Inhibiting ethylene perception with 1-methylcyclopropene triggers molecular responses aimed to cope with cell toxicity and increased respiration in citrus fruits

“…The use of this reference sample has been widely used in Citrus transcriptomic research since represent a powerful tool for reducing the number of hybridizations to make all the possible pairwise comparisons between samples (Ballester et al, 2011;Romero et al, 2012). SAM (Significant Analysis of Microarrays), included in the TM4 Microarray Software Suite, was used to identify differentially expressed genes using a False Discovery Rate threshold pvalue < 0.01 as previously described (Ballester et al, 2011;Romero et al, 2012). FatiGOþ (Babelomics, http://babelomics.bioinfo.cipf.…”

Interaction Between ABA Signaling and Copper Homeostasis inArabidopsis thaliana

“…The amount of RNA was measured by a spectrophotometric analysis and its quality was verified by agarose gel electrophoresis and ethidium bromide staining. Reverse transcription, followed by a quantitative PCR analysis (qRT-PCR), was performed and designed according to Romero et al (2012). Gene-specific primers were designed with the Primer3 software (http://bioinfo.ut.ee/primer3-0.4.0).…”

“…Indeed an ABA-deficient citrus mutant, prone to fruit dehydration, has been reported to be incapable of inducing similar early molecular responses to mild water stress to those observed in wild-type (WT) fruit (Romero et al 2012). Some differential transcriptomic responses among cultivars have been related to Cu homeostasis, such as the expression of COPT1, COPT2 and COPT5, which were induced in parental, but not in the ABA-deficient, citrus fruit (Romero et al 2012). This result supports the notion that the ABA/drought-mediated regulation of genes is involved in metal homeostasis.…”

Depletion of abscisic acid levels in roots of flooded Carrizo citrange (Poncirus trifoliata L. Raf. × Citrus sinensis L. Osb.) plants is a stress-specific response associated to the differential expression of PYR/PYL/RCAR receptors

“…The physiological processes regulated by ABA need to be modulated according to the pressure of the stress exerted and the pre-existing physiological status of the plant (Arbona and Gómez-Cadenas 2008;Romero et al 2012b). This implies a fine adjustment of the magnitude of the physiological response and requires a more complex regulatory system than the sole presence/absence of ABA.…”

“…Indeed, there are 14 loci encoding for ABA receptors in Arabidopsis, each of them having different intrinsic affinities for the hormone and could also bind to specific PP2Cs (Dupeux et al 2011;Santiago et al 2012;Antoni et al 2013;Fuchs et al 2014). Besides the fine-tuning of the ABA signal, modulation of the endogenous hormone levels is associated to the specific environmental situation and the stress pressure, which adds further complexity to the model (Seiler et al 2011;Romero et al 2012b; Baron et al 2012;De Ollas et al 2013). …”