Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India.
Plant Physiol. 2013 Apr;161(4):2085-101. doi: 10.1104/pp.112.212191. Epub 2013 Feb 11.
Tomato (Solanum lycopersicum) high-pigment mutants with lesions in diverse loci such as DNA Damage-Binding Protein1 (high pigment1 [hp1]), Deetiolated1 (hp2), Zeaxanthin Epoxidase (hp3), and Intense pigment (Ip; gene product unknown) exhibit increased accumulation of fruit carotenoids coupled with an increase in chloroplast number and size. However, little is known about the underlying mechanisms exaggerating the carotenoid accumulation and the chloroplast number in these mutants. A comparison of proteome profiles from the outer pericarp of hp1 mutant and wild-type (cv Ailsa Craig) fruits at different developmental stages revealed at least 72 differentially expressed proteins during ripening. Hierarchical clustering grouped these proteins into three clusters. We found an increased abundance of chromoplast-specific carotenoid-associated protein (CHRC) in hp1 fruits at red-ripe stage that is also reflected in its transcript level. Western blotting using CHRC polyclonal antibody from bell pepper (Capsicum annuum) revealed a 2-fold increase in the abundance of CHRC protein in the red-ripe stage of hp1 fruits compared with the wild type. CHRC levels in hp2 were found to be similar to that of hp1, whereas hp3 and Ip showed intermediate levels to those in hp1, hp2, and wild-type fruits. Both CHRC and carotenoids were present in the isolated plastoglobules. Overall, our results suggest that loss of function of DDB1, DET1, Zeaxanthin Epoxidase, and Ip up-regulates CHRC levels. Increase in CHRC levels may contribute to the enhanced carotenoid content in these high-pigment fruits by assisting in the sequestration and stabilization of carotenoids.
番茄（Solanum lycopersicum）高色素突变体在不同基因座（如 DNA 损伤结合蛋白 1（高色素 1[hp1]）、去黄化 1（hp2）、玉米黄质环氧化酶（hp3）和强色素（Ip；基因产物未知））发生病变，表现出果实类胡萝卜素积累增加，同时叶绿体数量和大小增加。然而，对于这些突变体中夸大类胡萝卜素积累和叶绿体数量的潜在机制知之甚少。hp1 突变体和野生型（cv Ailsa Craig）果实外果皮在不同发育阶段的蛋白质组图谱比较显示，在成熟过程中有至少 72 种差异表达蛋白。层次聚类将这些蛋白分为三组。我们发现 hp1 果实的红色成熟阶段中质体特异性类胡萝卜素相关蛋白（CHRC）的丰度增加，这也反映在其转录水平上。使用来自甜椒（Capsicum annuum）的 CHRC 多克隆抗体进行 Western blot 分析显示，与野生型相比，hp1 果实红色成熟阶段 CHRC 蛋白的丰度增加了 2 倍。发现 hp2 的 CHRC 水平与 hp1 相似，而 hp3 和 Ip 则显示出与 hp1、hp2 和野生型果实相似的中等水平。CHRC 和类胡萝卜素都存在于分离的质体小球中。总的来说，我们的结果表明 DDB1、DET1、玉米黄质环氧化酶和 Ip 的功能丧失会增加 CHRC 水平。CHRC 水平的增加可能通过协助类胡萝卜素的隔离和稳定来促进这些高色素果实中类胡萝卜素含量的增加。
