Zou Zhi, Zheng Yujiao, Zhang Zhongtian, Xiao Yanhua, Xie Zhengnan, Chang Lili, Zhang Li, Zhao Yongguo
Hainan Key Laboratory for Biosafety Monitoring and Molecular Breeding in Off-Season Reproduction Regions, Institute of Tropical Biosciences and Biotechnology/Sanya Research Institute of Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, Hainan, People's Republic of China.
Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Science, South-Central Minzu University, Wuhan, 430074, Hubei, People's Republic of China.
Plant Cell Rep. 2023 Nov;42(11):1791-1808. doi: 10.1007/s00299-023-03066-x. Epub 2023 Sep 25.
CeOLE genes exhibit a tuber-predominant expression pattern and their mRNA/protein abundances are positively correlated with oil accumulation during tuber development. Overexpression could significantly increase the oil content of tobacco leaves. Oleosins (OLEs) are abundant structural proteins of lipid droplets (LDs) that function in LD formation and stabilization in seeds of oil crops. However, little information is available on their roles in vegetative tissues. In this study, we present the first genome-wide characterization of the oleosin family in tigernut (Cyperus esculentus L., Cyperaceae), a rare example accumulating high amounts of oil in underground tubers. Six members identified represent three previously defined clades (i.e. U, SL and SH) or six out of seven orthogroups (i.e. U, SL1, SL2, and SH1-3) proposed in this study. Comparative genomics analysis reveals that lineage-specific expansion of Clades SL and SH was contributed by whole-genome duplication and dispersed duplication, respectively. Moreover, presence of SL2 and SH3 in Juncus effuses implies their appearance sometime before Cyperaceae-Juncaceae divergence, whereas SH2 appears to be Cyperaceae specific. Expression analysis showed that CeOLE genes exhibit a tuber-predominant expression pattern and transcript levels are considerably more abundant than homologs in the close relative Cyperus rotundus. Moreover, CeOLE mRNA and protein abundances were shown to positively correlate with oil accumulation during tuber development. Additionally, two dominant isoforms (i.e. CeOLE2 and -5) were shown to locate in LDs as well as the endoplasmic reticulum of tobacco (Nicotiana benthamiana) leaves, and are more likely to function in homo and heteromultimers. Furthermore, overexpression of CeOLE2 and -5 in tobacco leaves could significantly increase the oil content, supporting their roles in oil accumulation. These findings provide insights into lineage-specific family evolution and putative roles of CeOLE genes in oil accumulation of vegetative tissues, which facilitate further genetic improvement for tigernut.
CeOLE基因呈现出块茎主导的表达模式，其mRNA/蛋白质丰度与块茎发育过程中的油脂积累呈正相关。过表达可显著提高烟草叶片的油脂含量。油质蛋白（OLEs）是脂滴（LDs）中丰富的结构蛋白，在油料作物种子的脂滴形成和稳定中发挥作用。然而，关于它们在营养组织中的作用，目前所知甚少。在本研究中，我们首次对荸荠（莎草科荸荠属，Cyperus esculentus L.）中的油质蛋白家族进行了全基因组特征分析，荸荠是一种罕见的在地下块茎中积累大量油脂的例子。鉴定出的六个成员代表了先前定义的三个进化枝（即U、SL和SH）或本研究中提出的七个直系同源组中的六个（即U、SL1、SL2和SH1 - 3）。比较基因组学分析表明，SL和SH进化枝的谱系特异性扩张分别是由全基因组复制和分散复制导致的。此外，灯心草中存在SL2和SH3意味着它们在莎草科 - 灯心草科分化之前就已出现，而SH2似乎是莎草科特有的。表达分析表明，CeOLE基因呈现出块茎主导的表达模式，转录水平比近缘种圆叶莎草中的同源基因丰富得多。此外，CeOLE mRNA和蛋白质丰度与块茎发育过程中的油脂积累呈正相关。此外，两种主要的异构体（即CeOLE2和 - 5）定位于烟草（本氏烟草）叶片的脂滴以及内质网中，并且更有可能在同多聚体和异多聚体中发挥作用。此外，CeOLE2和 - 5在烟草叶片中的过表达可显著提高油脂含量，支持了它们在油脂积累中的作用。这些发现为谱系特异性家族进化以及CeOLE基因在营养组织油脂积累中的假定作用提供了见解，这有助于荸荠的进一步遗传改良。
