Genome-wide analysis revealed the stepwise origin and functional diversification of HSDs from lower to higher plant species

Abstract

Hydroxysteroid dehydrogenase (HSDs) is an oil-body sterol protein (steroleosin) with an NADP(H) binding domain that belongs to the short-chain dehydrogenase/reductase (SDR) superfamily. There are numerous studies on the characterization of HSDs in plants. However, thus far, the evolutionary differentiation and divergence analysis of these genes remain to be explored. The current study used an integrated method to elucidate the sequential evolution of HSDs in 64 sequenced plant genomes. Analyses were conducted on their origins, distribution, duplication, evolutionary paths, domain functions, motif composition, properties, and cis-elements. Results indicate that except for algae, HSD1 was widely distributed in plant species ranging from lower to higher plants, while HSD5 was restricted to terrestrial plants, and HSD2 was identified in fewer monocots and several dicot plants. Phylogenetic analysis of HSD proteins revealed that monocotyledonous HSD1 in moss and ferns appeared closest to the outgroup, V. carteri HSD-like, M. musculus HSD1, and H. sapiens HSD1. These data support the hypothesis that HSD1 originated in bryophytes and then in non-vascular and vascular plants, followed by HSD5 only in land plants. Gene structure analysis suggests that HSDs in plant species came up with a fixed number of six exons, and the intron phase was primarily 0, 1, 0, 0, and 0. Similarly, duplication analysis revealed that segmental duplications were the main reason for HSDs in plant species. Physicochemical properties suggest that dicotyledonous HSD1s and HSD5s were mainly acidic. The monocotyledonous HSD1s and HSD2s and the dicotyledonous HSD2s, HSD3s, HSD4s, and HSD6s were mainly basic, implying that HSDs in plants may have a variety of functions. Cis-regulatory elements and expression analysis revealed that HSDs in plants might have roles in several abiotic stresses. Due to the high expression of HSD1s and HSD5s in seeds, these HSDs in plants may have roles in fatty acid accumulation and degradation.

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 ].…”