School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, UK.
Syngenta, Jealott's Hill International Research Centre, Bracknell, Berkshire, UK.
J Exp Bot. 2019 May 9;70(10):2637-2650. doi: 10.1093/jxb/erz086.
The exploitation of diverse natural variation has been a key progenitor of crop breeding over the last decade. However, commercial practice is now turning to the use of accessions with less extreme phenotypes as genetic donors. In the present study, the carotenoid formation in a red-fruited discovery panel of Capsicum annuum (chilli pepper) has been characterized. The data indicated that colour intensity correlated with the amount of capsanthin and its esters, along with transcript levels of the 1-deoxy-d-xylulose 5-phosphate synthase (DXS) and phytoene synthase-1 (PSY-1) genes. Quantification of carotenoids through development and ripening suggested the presence of separate biosynthesis and accumulation phases. Subplastid fractionation demonstrated the differential sequestration of pigments in high- and low-intensity lines and revealed the PSY protein to be most active in the membrane fractions when abundance was highest in the fibril fractions. Carotenoid accumulation was associated with the esterification of xanthophylls, expression of a putative carotenoid acyl transferase, and increased fibril content within the plastid. Interrogation of TEM images and carotenoid analysis of subplastid fractions suggest that the plastoglobuli are likely to be the progenitor of the characteristic fibrils found in pepper fruit. Collectively, these data provide an insight into the underpinning molecular, biochemical, and cellular mechanisms associated with the synthesis and sequestration of carotenoids in chromoplast-containing fruits, in addition to providing potential tools and resources for the breeding of high red colour intensity pepper varieties.
在过去十年中，利用多样化的自然变异一直是作物育种的关键。然而，商业实践现在转向使用表型不那么极端的品系作为遗传供体。在本研究中，对辣椒（辣椒）的红色果实发现面板中的类胡萝卜素形成进行了表征。数据表明，颜色强度与辣椒素及其酯的含量以及 1-脱氧-d-木酮糖 5-磷酸合酶（DXS）和八氢番茄红素合酶-1（PSY-1）基因的转录水平相关。通过发育和成熟对类胡萝卜素进行定量表明，存在单独的生物合成和积累阶段。亚质体分级分离表明在高强度和低强度品系中色素的差异隔离，并显示 PSY 蛋白在膜部分中最活跃，当丰度在原纤维部分中最高时。类胡萝卜素的积累与叶黄素的酯化、假定的类胡萝卜素酰基转移酶的表达以及质体中原纤维含量的增加有关。对 TEM 图像的询问和亚质体部分的类胡萝卜素分析表明，质体小球体可能是胡椒果实中特征性原纤维的前体。总的来说，这些数据提供了对与富含类胡萝卜素的质体中类胡萝卜素合成和隔离相关的分子、生化和细胞机制的深入了解，此外还为培育高红色强度的辣椒品种提供了潜在的工具和资源。
