Identification and Analysis of Expression Patterns of the Caleosin Genes in Hickory (Carya cathayensis Sarg.)

Abstract

The deciduous tree hickory (Carya cathayensis) holds economic significance in China due to its high oil content, particularly in unsaturated fatty acids. Oil bodies are crucial for storing triacylglycerol (TAG), with caleosin serving as a predominant oil body protein that aids in oil body formation and stability maintenance. Our study utilized bioinformatics techniques to identify caleosin genes within Carya cathayensis, Carya illinoinensis, and Juglans regia. Three caleosin genes were discovered in the genomes of Carya cathayensis, Carya illi-noinensis, and Juglans regia. These genes encode hydrophilic proteins. Additionally, all caleosin proteins feature a single Ca2+-binding EF-hand, a conserved “proline knot” motif, and a C-terminal hydrophilic region with four potential phosphorylation sites. The caleosin proteins in Carya cathayensis consist of α-helix, β-corner, extended chain, and random curl structures. Cis-acting elements related to stress response and hormone signaling were identified in Carya cathayensis, Carya illinoinensis, and Juglans regia, with distinct cis-acting elements implicated in seed-specific regulation in Carya cathayensis. Additionally, subcellular localization analysis confirmed that CcaCLO1 and CcaCLO2 were localized within oil bodies. Transcriptome analysis and quantitative real-time polymerase chain reaction (qRT-PCR) data demonstrated a significant up-regulation of CcaCLO1 expression during the developmental stages of the Carya cathayensis embryo. Furthermore, qPCR findings indicated that caleosins from Carya cathayensis were responsive to salt stress, with a significant up-regulation of CcaCLO1 following exposure to salt stress treatment. Consequently, caleosin genes in Carya cathayensis, Carya illinoinensis, and Juglans regia share similar physicochemical characteristics and conserved motifs. Specifically, CcaCLO1 in Carya cathayensis primarily responds to embryo development and salt stress. These findings offer foundational insights for future investigations into the regulatory mechanisms of oil accumulation and response to salt stress in hickory.

Exploring selection signatures in the divergence and evolution of lipid droplet (LD) associated genes in major oilseed crops

“…Likewise, oleosins are the LD-specific plant proteins that are involved in myriads of physiological processes like seed germination, lipid metabolism, stress response, hormone signaling, seed oil content enhancement, storage lipid stability and rancidity [ 13 , 17 , 18 ]. Caleosins, steroleosins are aslo included in the phospholipid monolayer of LDs in addition to oleosins [ 20 , 21 ] while SEIPINS are also involved in lipid droplet organization and lipid metabolism [ 22 ] in addition to seed germination and maturity. Furthermore, TAG lipases are actively involved in seed germination, lipid metabolism, membrane lipid remodeling, stress response, LD biogenesis, and oil rancidity [ 48 – 50 , and 51 ].…”

“…Moreover, oleosins are directly involved in seed oil accumulation as reported in B. napus and A. thaliana [ 18 , 19 ]. In addition, caleosins (CLO/PXG) the calcium binding oil surface body protein [ 20 ], steroleosins (HSD) known as sterol dehydrogenases [ 21 ] and SEIPINs encoding integral membrane proteins are crucial for LD biogenesis and organization in close association with oleosins [ 22 ]. TAG lipases like SDP1 are actively involved in germination through lipid degradation while silencing of the gene leads to increased oil content [ 23 ].…”