Citrus ABA signalosome: identification and transcriptional regulation during sweet orange fruit ripening and leaf dehydration

• Published in: Journal of experimental botany Vol. 63; no. 13; pp. 4931 - 4945
• Main Authors: Romero, Paco, Lafuente, María T, Rodrigo, María J
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press [etc.] 01-08-2012; Oxford University Press
• Subjects: abscisic acid; Abscisic Acid - analysis; Abscisic Acid - metabolism; Arabidopsis; Biological and medical sciences; Citrus; Citrus sinensis - genetics; Citrus sinensis - growth & development; Citrus sinensis - physiology; correlation; cultivars; Dehydration; Fruit - genetics; Fruit - growth & development; Fruit - physiology; fruiting; Fundamental and applied biological sciences. Psychology; gene expression; Gene Expression Regulation, Plant - genetics; genes; Genome, Plant - genetics; leaves; mutants; Mutation; oranges; Phylogeny; Plant Leaves - genetics; Plant Leaves - growth & development; Plant Leaves - physiology; Plant physiology and development; Plant Proteins - genetics; Plant Proteins - metabolism; protein folding; protein kinases; receptors; Research Paper; ripening; Signal Transduction; transcription (genetics); water stress; Citrus sinensis; Transcription; PYR/PYL/RCAR; Citrus fruit; Rutaceae; Dehydration; fruit ripening; Orange; leaf dehydration; Dicotyledones; Sesquiterpenes; Angiospermae; Botany; Abscisic acid; Plant growth substance; Transcription factor; PP2CA; signalling; Fruit; Abscisic acid (ABA); Plant leaf; Gene expression; Ripening; Citrus; receptor; Spermatophyta; SnRK2
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/ers168

The abscisic acid (ABA) signalling core in plants include the cytosolic ABA receptors (PYR/PYL/RCARs), the clade-A type 2C protein phosphatases (PP2CAs), and the subclass III SNF1-related protein kinases 2 (SnRK2s). The aim of this work was to identify these ABA perception system components in sweet orange and to determine the influence of endogenous ABA on their transcriptional regulation during fruit development and ripening, taking advantage of the comparative analysis between a wild-type and a fruit-specific ABA-deficient mutant. Transcriptional changes in the ABA signalosome during leaf dehydration were also studied. Six PYR/PYL/RCAR, five PP2CA, and two subclass III SnRK2 genes, homologous to those of Arabidopsis, were identified in the Citrus genome. The high degree of homology and conserved motifs for protein folding and for functional activity suggested that these Citrus proteins are bona fide core elements of ABA perception in orange. Opposite expression patterns of CsPYL4 and CsPYL5 and ABA accumulation were found during ripening, although there were few differences between varieties. In contrast, changes in expression of CsPP2CA genes during ripening paralleled those of ABA content and agreeed with the relevant differences between wild-type and mutant fruit transcript accumulation. CsSnRK2 gene expression continuously decreased with ripening and no remarkable differences were found between cultivars. Overall, dehydration had a minor effect on CsPYR/PYL/RCAR and CsSnRK2 expression in vegetative tissue, whereas CsABI1, CsAHG1, and CsAHG3 were highly induced by water stress. The global results suggest that responsiveness to ABA changes during citrus fruit ripening, and leaf dehydration was higher in the CsPP2CA gene negative regulators than in the other ABA signalosome components.