Liu Bei, Zhang Di, Sun Ming, Li Manli, Ma Xiqing, Jia Shangang, Mao Peisheng
Forage Seed Laboratory, College of Grassland Science and Technology, China Agricultural University, Beijing 100193, China.
Key Laboratory of Pratacultural Science, Beijing Municipality, Yuanmingyuan West Road, Haidian District, Beijing 100193, China.
Int J Mol Sci. 2021 May 17;22(10):5258. doi: 10.3390/ijms22105258.
The color of bracts generally turns yellow or black from green during cereal grain development. However, the impact of these phenotypic changes on photosynthetic physiology during black bract formation remains unclear. Two oat cultivars ( L.), 'Triple Crown' and 'Qinghai 444', with yellow and black bracts, respectively, were found to both have green bracts at the heading stage, but started to turn black at the flowering stage and become blackened at the milk stage for 'Qinghai 444'. Their photosynthetic characteristics were analyzed and compared, and the key genes, proteins and regulatory pathways affecting photosynthetic physiology were determined in 'Triple Crown' and 'Qinghai 444' bracts. The results show that the actual PSII photochemical efficiency and PSII electron transfer rate of 'Qinghai 444' bracts had no significant changes at the heading and milk stages but decreased significantly ( < 0.05) at the flowering stage compared with 'Triple Crown'. The chlorophyll content decreased, the LHCII involved in the assembly of supercomplexes in the thylakoid membrane was inhibited, and the expression of and was downregulated at the flowering stage. During this critical stage, the expression of and was upregulated, and the biosynthetic pathway of -coumaric acid using tyrosine and phenylalanine as precursors was also enhanced. Moreover, the key upregulated genes (, and ) of anthocyanin biosynthesis might complement the impaired PSII activity until recovered at the milk stage. These findings provide a new insight into how photosynthesis alters during the process of oat bract color transition to black.
在谷物籽粒发育过程中，苞片颜色通常会从绿色变为黄色或黑色。然而，这些表型变化对黑色苞片形成过程中光合生理的影响尚不清楚。研究发现，两个燕麦品种（L.），分别为苞片黄色的“三冠王”和苞片黑色的“青海444”，在抽穗期苞片均为绿色，但在开花期“青海444”开始变黑，并在乳熟期完全变黑。对它们的光合特性进行了分析和比较，并确定了影响“三冠王”和“青海444”苞片光合生理的关键基因、蛋白质和调控途径。结果表明，“青海444”苞片在抽穗期和乳熟期的实际PSII光化学效率和PSII电子传递速率无显著变化，但与“三冠王”相比，在开花期显著降低（<0.05）。叶绿素含量降低，参与类囊体膜超复合体组装的LHCII受到抑制，在开花期 和 的表达下调。在这个关键阶段， 和 的表达上调，以酪氨酸和苯丙氨酸为前体的对香豆酸生物合成途径也增强。此外，花青素生物合成的关键上调基因（ 、 和 ）可能会补充受损的PSII活性，直到在乳熟期恢复。这些发现为燕麦苞片颜色转变为黑色过程中光合作用如何变化提供了新的见解。
