Abscisic acid deficiency caused by phytoene desaturase silencing is associated with dwarfing syndrome in citrus
In citrus, abscisic acid-deficiency was associated with a dwarfing phenotype, slow growth, small leaves, decreased fresh weight, and faster water loss. ABA supplementation reversed the dwarfing phenotype and enhanced growth.
Abscisic acid (ABA) is a ubiquitously distributed phytohormone, which is almost produced by all living kingdoms. In plants, ABA plays pleiotropic physiological roles in growth, development, and stress responses. We explored the hidden relationship between ABA deficiency, and citrus dwarfing. We used targeted-HPLC, targeted-GC–MS, molecular genetics, immunoassays, and gene expression techniques to investigate the effects of the silencing of phytoene desaturase (PDS) gene on the ABA-biosynthetic pathway, endogenous ABA content, and other phytohormones. Silencing of PDS directly suppressed the carotenoids compounds involved in ABA biosynthesis, altered phytohormonal profile, and caused phytoene accumulation and ABA deficiency. The reduction of ABA presumably due to the limited availability of its precursor, zeaxanthin. The ABA-deficient citrus cuttings displayed photobleaching, a dwarf phenotype with impaired growth characteristics that included slow growth, small leaves, decreased fresh weight, and faster water loss. ABA supplementation enhanced the growth and reversed the dwarfing phenotype of the ABA-deficient cuttings. Our data demonstrate that ABA-deficiency may lead to dwarfing phenotype and impaired growth in citrus cuttings. The negative influence of ABA-deficiency on growth rate is the result of altered water relations. Addition of ABA to the CTV-tPDS roots restored shoot growth and reversed the dwarfing phenotype.
KeywordsCitrus sinensis Phytoene desaturase Abscisic acid Virus-induced gene silencing Dwarfing
The authors acknowledge our CREC colleagues for their helpful discussion. We thank Dr. Faraj Hijaz and Shelley E. Jones for the technical assistance and Floyd Butz for maintaining the trees in greenhouses.
Author contribution statement
NK and YN conceptualized the research, performed experiments, conducted data analysis, visualized the data, and wrote the manuscript; NK administered the project.
Compliance with ethical standards
Conflict of interest
The authors declare no conflict of interest.
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