Leaf Tobacco Research Center, Japan Tobacco, Inc., 1900 Idei, Oyama, Tochigi, 323-0808, Japan.
Sci Rep. 2023 Aug 10;13(1):12992. doi: 10.1038/s41598-023-39692-4.
Apocarotenoid volatiles contribute to the flavor of many agricultural products. In many flowering plants, carotenoid cleavage dioxygenase 4 (CCD4) is involved in the decomposition of carotenoids and resultant production of C13-apocarotenoids, such as β-ionone derived from β-carotene. To understand the possible role of tobacco CCD4 genes (NtCCD4-S, NtCCD4-T1 and NtCCD4-T2) in these processes, we analyzed loss-of-function phenotypes. RNA interference transgenic plants showed yellow color in mature (senescent) leaves. Mature leaves of chemically induced double-mutant plants showed a stronger yellow color, and those of triple-mutant plants showed a pronounced yellow color. Carotenoid analysis of the leaves from mutants showed that lutein and β-carotene increased in line with the degree of color change compared to wild type, whereas there was little change in green color in their young leaves. This result indicates that CCD4s are important for the decomposition of carotenoids in the tobacco leaf maturation process. Analysis of apocarotenoids in flue-cured leaves of the multiple-mutant plants showed that many compounds, including megastigmatrienones, were decreased in comparison to wild type, whereas intriguingly β-ionone and dihydroactinidiolide were increased. Our results suggest that CCD4s play a key role in both carotenoid level and apocarotenoid composition in flue-cured mature tobacco leaves.
类胡萝卜素挥发物为许多农产品增添了风味。在许多开花植物中，类胡萝卜素裂解双加氧酶 4（CCD4）参与类胡萝卜素的分解以及 C13-类胡萝卜素的产生，如β-胡萝卜素衍生的β-紫罗兰酮。为了了解烟草 CCD4 基因（NtCCD4-S、NtCCD4-T1 和 NtCCD4-T2）在这些过程中的可能作用，我们分析了功能丧失表型。RNA 干扰转基因植物在成熟（衰老）叶片中表现出黄色。化学诱导的双突变体植物的成熟叶片表现出更强的黄色，而三突变体植物的成熟叶片则表现出明显的黄色。对突变体叶片的类胡萝卜素分析表明，与野生型相比，叶黄素和β-胡萝卜素的含量随着颜色变化的程度而增加，而其幼叶中的绿色变化不大。这一结果表明 CCD4 对于烟草叶片成熟过程中类胡萝卜素的分解很重要。对多突变体植物烤烟叶片的挥发物分析表明，与野生型相比，许多化合物，包括巨二烯酮，含量降低，而令人感兴趣的是，β-紫罗兰酮和二氢actinidiolide 增加。我们的结果表明，CCD4 在烤烟成熟叶片的类胡萝卜素水平和挥发物组成中都起着关键作用。
