Perrin Florent, Hartmann Laura, Dubois-Laurent Cécile, Welsch Ralf, Huet Sébastien, Hamama Latifa, Briard Mathilde, Peltier Didier, Gagné Séverine, Geoffriau Emmanuel
IRHS, Agrocampus Ouest, INRA, SFR QuaSaV, Université d'Angers, 49071, Beaucouzé, France.
Faculty of Biology II, University of Freiburg, Freiburg, Germany.
Planta. 2017 Apr;245(4):737-747. doi: 10.1007/s00425-016-2637-9. Epub 2016 Dec 20.
Main conclusion Variations in gene expression can partially explain the difference of carotenoid accumulation in secondary phloem and xylem of fleshy carrot roots. The carrot root is well divided into two different tissues separated by vascular cambium: the secondary phloem and xylem. The equilibrium between these two tissues represents an important issue for carrot quality, but the knowledge about the respective carotenoid accumulation is sparse. The aim of this work was (i) to investigate if variation in carotenoid biosynthesis gene expression could explain differences in carotenoid content in phloem and xylem tissues and (ii) to investigate if this regulation is differentially modulated in the respective tissues by water-restricted growing conditions. In this work, five carrot genotypes contrasting by their root color were studied in control and water-restricted conditions. Carotenoid content and the relative expression of 13 genes along the carotenoid biosynthesis pathway were measured in the respective tissues. Results showed that in orange genotypes and the purple one, carotenoid content was higher in phloem compared to xylem. For the red one, no differences were observed. Moreover, in control condition, variations in gene expression explained the different carotenoid accumulations in both tissues, while in water-restricted condition, no clear association between gene expression pattern and variations in carotenoid content could be detected except in orange-rooted genotypes. This work shows that the structural aspect of carrot root is more important for carotenoid accumulation in relation with gene expression levels than the consequences of expression changes upon water restriction.
主要结论 基因表达的变化可以部分解释肉质胡萝卜根次生韧皮部和木质部中类胡萝卜素积累的差异。胡萝卜根被维管形成层很好地分为两个不同的组织：次生韧皮部和木质部。这两个组织之间的平衡是影响胡萝卜品质的一个重要问题，但关于各自类胡萝卜素积累的知识却很匮乏。这项工作的目的是：（i）研究类胡萝卜素生物合成基因表达的变化是否可以解释韧皮部和木质部组织中类胡萝卜素含量的差异；（ii）研究在水分受限的生长条件下，这种调控在各自组织中是否受到不同的调节。在这项工作中，研究了五种根颜色不同的胡萝卜基因型在对照和水分受限条件下的情况。在各自的组织中测量了类胡萝卜素含量以及沿着类胡萝卜素生物合成途径的13个基因的相对表达。结果表明，在橙色基因型和紫色基因型中，韧皮部中的类胡萝卜素含量高于木质部。对于红色基因型，未观察到差异。此外，在对照条件下，基因表达的变化解释了两个组织中不同的类胡萝卜素积累情况，而在水分受限条件下，除了橙色根基因型外，未检测到基因表达模式与类胡萝卜素含量变化之间有明显关联。这项工作表明，与水分限制对表达变化的影响相比，胡萝卜根的结构方面对于与基因表达水平相关的类胡萝卜素积累更为重要。
