Abstract
BackgroundCotton is not only a major textile fiber crop but also a vital oilseed, industrial, and forage crop. Oleosins are the structural proteins of oil bodies, influencing their size and the oil content in seeds. In addition, the degradation of oleosins is involved in the mobilization of lipid and oil bodies during seed germination. However, comprehensive identification and the systematic analysis of the Oleosin gene (OLEOs) family have not been conducted in cotton.ResultsAn in-depth analysis has enabled us to identify 25 and 24 OLEOs in tetraploid cotton species G. hirsutum and G. barbadense, respectively, while 12 and 13 OLEOs were identified in diploid species G. arboreum and G. raimondii, respectively. The 74 OLEOs were further clustered into three lineages according to the phylogenetic tree. Synteny analysis revealed that most of the OLEOs were conserved and that WGD or segmental duplications might drive their expansion. The transmembrane helices in GhOLEO proteins were predicted, and three transmembrane models were summarized, in which two were newly proposed. A total of 24 candidate miRNAs targeting GhOLEOs were predicted. Three highly expressed oil-related OLEOs, GH_A07G0501 (SL), GH_D10G0941 (SH), and GH_D01G1686 (U), were cloned, and their subcellular localization and function were analyzed. Their overexpression in Arabidopsis increased seed oil content and decreased seed germination rates.ConclusionWe identified OLEO gene family in four cotton species and performed comparative analyses of their relationships, conserved structure, synteny, and gene duplication. The subcellular localization and function of three highly expressed oil-related OLEOs were detected. These results lay the foundation for further functional characterization of OLEOs and improving seed oil content.
Highlights
Cotton is a major textile fiber crop and a vital oilseed, industrial, and forage crop
Whole‐genome identification and characterization of Oleosin genes in four cotton species Combined with the results of BLASTP search, HMMER analysis, and Conserved domain database (CDD) check, a total of 25, 24, 12, and 13 Oleosins were identified in two tetraploids, G. hirsutum and G. barbadense, and two diploids, G. arboreum and G. raimondii, respectively
The results showed that the yellow fluorescent signals, which was the composite light of green (GFP) and red (Nile red), were present in the membrane of oil bodies in the merged fields of the three fusion proteins (Fig. 7), indicating that the Seed low-molecular-weight lineage (SL), Seed high-molecularweight lineage (SH), and U oleosin protein might be located on the oil body membrane
Summary
Cotton is a major textile fiber crop and a vital oilseed, industrial, and forage crop. Oleosins are the structural proteins of oil bodies, influencing their size and the oil content in seeds. The degradation of oleosins is involved in the mobilization of lipid and oil bodies during seed germination. The oil body is approximately 0.5-2 μm in diameter and has the basic structure that a core of neutral lipids surrounded by the phospholipid monolayer with specific proteins [4]. The specific proteins in oil bodies, mainly oleosin, caleosin, and steroleosin, have been shown to play an essential role in regulating oil body size and number and lipid accumulation [5, 6]. Oleosins account for 80-90% of the structural proteins in OBs and play a key role in lipid storage [7]. The Oleosin (OLEO) gene sequence was first identified and characterized in maize [8] and cloned in various plants, including rapeseed [9], sesame [10], soybean [11], rice [12], sunflower [13]
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