Departamento de Mejora Genética Vegetal, Instituto de Agricultura Sostenible-Consejo Superior de Investigaciones Scientificas, Córdoba, Spain.
PLoS One. 2011;6(5):e19885. doi: 10.1371/journal.pone.0019885. Epub 2011 May 16.
The wild barley Hordeum chilense Roem. et Schult. is a valuable source of genes for increasing carotenoid content in wheat. Tritordeums, the amphiploids derived from durum or common wheat and H. chilense, systematically show higher values of yellow pigment colour and carotenoid content than durum wheat. Phytoene synthase 1 gene (Psy1) is considered a key step limiting the carotenoid biosynthesis, and the correlation of Psy1 transcripts accumulation and endosperm carotenoid content has been demonstrated in the main grass species.
METHODOLOGY/PRINCIPAL FINDINGS: We analyze the variability of Psy1 alleles in three lines of H. chilense (H1, H7 and H16) representing the three ecotypes described in this species. Moreover, we analyze Psy1 expression in leaves and in two seed developing stages of H1 and H7, showing mRNA accumulation patterns similar to those of wheat. Finally, we identify thirty-six different transcripts forms originated by alternative splicing of the 5' UTR and/or exons 1 to 5 of Psy1 gene. Transcripts function is tested in a heterologous complementation assay, revealing that from the sixteen different predicted proteins only four types (those of 432, 370, 364 and 271 amino acids), are functional in the bacterial system.
CONCLUSIONS/SIGNIFICANCE: The large number of transcripts originated by alternative splicing of Psy1, and the coexistence of functional and non functional forms, suggest a fine regulation of PSY activity in H. chilense. This work is the first analysis of H. chilense Psy1 gene and the results reported here are the bases for its potential use in carotenoid enhancement in durum wheat.
野生大麦 Hordeum chilense Roem. et Schult. 是提高小麦类胡萝卜素含量的基因的宝贵来源。衍生自硬质小麦或普通小麦与 H. chilense 的三属种，系统地表现出比硬质小麦更高的黄色素颜色和类胡萝卜素含量值。八氢番茄红素合酶 1 基因（Psy1）被认为是限制类胡萝卜素生物合成的关键步骤，并且在主要禾本科植物中已经证明了 Psy1 转录物积累与胚乳类胡萝卜素含量之间的相关性。
方法/主要发现：我们分析了代表该物种中描述的三种生态型的三种 H. chilense 品系（H1、H7 和 H16）中 Psy1 等位基因的变异性。此外，我们分析了 H1 和 H7 中两个种子发育阶段的 Psy1 表达，显示出与小麦相似的 mRNA 积累模式。最后，我们鉴定了 Psy1 基因的 5'UTR 和/或外显子 1 到 5 的选择性剪接产生的三十六个不同转录本形式。通过异源互补测定测试了转录本的功能，表明在十六种不同预测的蛋白质中，只有四种类型（432、370、364 和 271 个氨基酸的类型）在细菌系统中具有功能。
结论/意义：由 Psy1 选择性剪接产生的大量转录本，以及功能和非功能形式的共存，表明在 H. chilense 中 PSY 活性受到精细调控。这项工作是对 H. chilense Psy1 基因的首次分析，这里报告的结果为其在硬质小麦中增强类胡萝卜素的潜在用途奠定了基础。
