A sunflower WRKY transcription factor stimulates the mobilization of seed-stored reserves during germination and post-germination growth
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The sunflower transcription factor HaWRKY10 stimulates reserves mobilization in Arabidopsis. Gene expression and enzymes activity assays indicated that lipolysis and gluconeogenesis were increased. Microarray results suggested a parallelism in sunflower.
Germinating oilseeds converts stored lipids into sugars, and thereafter in metabolic energy that is used in seedling growth and establishment. During germination, the induced lipolysis linked to the glyoxylate pathway and gluconeogenesis produces sucrose, which is then transported to the embryo and driven through catabolic routes. Herein, we report that the sunflower transcription factor HaWRKY10 regulates carbon partitioning by reducing carbohydrate catabolism and increasing lipolysis and gluconeogenesis. HaWRKY10 was regulated by abscisic acid and gibberellins in the embryo leaves 48 h after seed imbibition and highly expressed during sunflower seed germination and seedling growth, concomitantly with lipid mobilization. Sunflower leaf disks overexpressing HaWRKY10 showed repressed expression of genes related to sucrose cleavage and glycolysis compared with controls. Moreover, HaWRKY10 constitutive expression in Arabidopsis seeds produced higher decrease in lipid reserves, whereas starch and sucrose were more preserved compared with wild type. Gene transcripts abundance and enzyme activities involved in stored lipid mobilization and gluconeogenesis increased more in transgenic than in wild type seeds 36 h after imbibition, whereas the negative regulator of lipid mobilization, ABI4, was repressed. Altogether, the results point out a functional parallelism between tissues and plant species, and reveal HaWRKY10 as a positive regulator of storage reserve mobilization in sunflower.
KeywordsSunflower Reserves mobilization Germination Arabidopsis Transcription factor WRKY
This work was supported by Agencia Nacional de Promoción Científica y Tecnológica [ANPCyT, PICT-PAE-37100, PICT-2011-850, PICT-2012-2439], Consejo Nacional de Investigaciones Científicas y Técnicas [CONICET, PIP 2011 11420100100278] and Universidad Nacional del Litoral [UNL, CAID 2011 50120110100349 and 50120110100399]. JR was a Fellow and MDH is a Fellow of CONICET and members of UNL; RLC, AAI and KFR are career members of CONICET and UNL.
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Conflict of interest
The authors declare that they have no conflict of interest.
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