Plant P4-ATPase lipid flippases: How are they regulated?

Genome-wide identification of the P4ATPase gene family and its response to biotic and abiotic stress in soybean (Glycine max L.)

BACKGROUND

Soybean is an important legume crop and has significant agricultural and economic value. P4-ATPases (aminophospholipid ATPases, ALAs), one of the classes of P-type ATPases, can transport or flip phospholipids across membranes, creating and maintaining lipid asymmetry and playing crucial roles in plant growth and development. To date, however, the ALA gene family and its expression patterns under abiotic and biotic stresses have not been studied in the soybean genome.

RESULTS

A total of 27 GmALA genes were identified in the soybean genome and these genes were unevenly distributed on 15 chromosomes and classified into five groups based on phylogenetic analysis. The GmALAs family had diverse intron-exon patterns and a highly conserved motif distribution. A total of eight domains were found in GmALAs, and all GmALAs had conserved PhoLip_ATPase_C, phosphorylation and transmembrane domains. Cis-acting elements in the promoter demonstrated that GmALAs are associated with cellular development, phytohormones, environmental stress and photoresponsiveness. Analysis of gene duplication events revealed 24 orthologous gene pairs in soybean and synteny analysis revealed that GmALAs had greater collinearity with AtALAs than with OsALAs. Evolutionary constraint analyses suggested that GmALAs have undergone strong selective pressure for purification during the evolution of soybeans. Tissue-specific expression profiles revealed that GmALAs were differentially expressed in roots, stems, seeds, flowers, nodules and leaves. The expression pattern of these genes appeared to be diverse in the different developmental tissues. Combined transcriptome and qRT-PCR data confirmed the differential expression of GmALAs under abiotic (dehydration, saline, low temperature, ozone, light, wounding and phytohormones) and biotic stresses (aphid, fungi, rhizobia and rust pathogen).

CONCLUSION

In summary, genome-wide identification and evolutionary and expression analyses of the GmALAs gene family in soybean were conducted. Our work provides an important theoretical basis for further understanding GmALAs in biological functional studies.

The role of interplay between the plant plasma membrane H+-ATPase and its lipid environment

The mechanisms behind the regulation of plasma membrane (PM) P-type H+-ATPase in plant cells mediated by lipid-protein interactions and lateral heterogeneity of the plasma membrane are discussed. This review will focus on 1) the structural organization and mechanisms of the catalytic cycle of the enzyme, 2) phosphorylation as the primary mechanism of pump regulation; 3) the possible role of lateral heterogeneity of the plasma membrane in this process, as well as 4) the role of lipids in the H+-ATPase biosynthesis and its delivery to the plasma membrane. In addition, 5) the potential role of membrane lipids in the H+-ATPase co-localisation with secondary active transporters is speculated.

Substrates, regulation, cellular functions, and disease associations of P4-ATPases

P4-ATPases, a subfamily of the P-type ATPase superfamily, play a crucial role in translocating membrane lipids from the exoplasmic/luminal leaflet to the cytoplasmic leaflet. This process generates and regulates transbilayer lipid asymmetry. These enzymes are conserved across all eukaryotes, and the human genome encodes 14 distinct P4-ATPases. Initially identified as aminophospholipid translocases, P4-ATPases have since been found to translocate other phospholipids, including phosphatidylcholine, phosphatidylinositol, and even glycosphingolipids. Recent advances in structural analysis have significantly improved our understanding of the lipid transport machinery associated with P4-ATPases, as documented in recent reviews. In this review, we highlight the emerging evidence related to substrate diversity, the regulation of cellular localization, enzymatic activities, and their impact on organism homeostasis and diseases.

Uptake and Metabolic Conversion of Exogenous Phosphatidylcholines Depending on Their Acyl Chain Structure in Arabidopsis thaliana

Fungi and plants are not only capable of synthesizing the entire spectrum of lipids de novo but also possess a well-developed system that allows them to assimilate exogenous lipids. However, the role of structure in the ability of lipids to be absorbed and metabolized has not yet been characterized in detail. In the present work, targeted lipidomics of phosphatidylcholines (PCs) and phosphatidylethanolamines (PEs), in parallel with morphological phenotyping, allowed for the identification of differences in the effects of PC molecular species introduced into the growth medium, in particular, typical bacterial saturated (14:0/14:0, 16:0/16:0), monounsaturated (16:0/18:1), and typical for fungi and plants polyunsaturated (16:0/18:2, 18:2/18:2) species, on Arabidopsis thaliana. For comparison, the influence of an artificially synthesized (1,2-di-(3-(3-hexylcyclopentyl)-propanoate)-sn-glycero-3-phosphatidylcholine, which is close in structure to archaeal lipids, was studied. The phenotype deviations stimulated by exogenous lipids included changes in the length and morphology of both the roots and leaves of seedlings. According to lipidomics data, the main trends in response to exogenous lipid exposure were an increase in the proportion of endogenic 18:1/18:1 PC and 18:1_18:2 PC molecular species and a decrease in the relative content of species with C18:3, such as 18:3/18:3 PC and/or 16:0_18:3 PC, 16:1_18:3 PE. The obtained data indicate that exogenous lipid molecules affect plant morphology not only due to their physical properties, which are manifested during incorporation into the membrane, but also due to the participation of exogenous lipid molecules in the metabolism of plant cells. The results obtained open the way to the use of PCs of different structures as cellular regulators.