The structure, functional evolution, and evolutionary trajectories of the H+-PPase gene family in plants

Systematic identification of sugarcane vacuolar H+-translocating pyrophosphatase (VPP) gene family and the role of ScVPP1 in salt resistance

KEY MESSAGE

A total of 24 genes of vacuolar H+-translocating pyrophosphatases H+-PPases (VPP) genes were identified in Saccharum spontaneum AP85-441 and the ScVPP1-overexpressed Arabidopsis plants conferred salt tolerance. The vital role of vacuolar H+-translocating pyrophosphatases H+-PPases (VPP) genes involved in plants in response to abiotic stresses. However, the understanding of VPP functions in sugarcane remained unclear. In this study, a total of 24 VPP genes (SsaVPP1-SsaVPP24) were identified in the Saccharum spontaneum genome of haploid clone AP85-441. These genes were distributed in two phylogenetic groups. The SsaVPPs displayed diverse physio-chemical and gene structure attributes. The SsaVPP family genes have expanded through segmental duplication (20 gene pairs) rather than tandem duplication. A full-length cDNA of ScVPP1 was cloned from the sugarcane cultivar ROC22 and shared 99.48% sequence identity (amino acid) with homologous gene SsaVPP21 from AP85-441. In ROC22, the ScVPP1 gene was considerably upregulated by NaCl and ABA treatments among leaf, root, and stem tissues, while this gene was exclusively upregulated in the root with PEG treatment. Under NaCl and ABA stresses, yeast cells transfected by the ScVPP1 plasmid showed distinct growth rates compared to control yeast cells transfected by the empty vector. In transgenic Arabidopsis lines overexpressing ScVPP1, the seed gemination and survival rate were enhanced under NaCl treatment but not under ABA stress as compared to wild-type plants. These results suggested that the ScVPP1 gene conferred tolerance to slat and may be used as a salt resistance gene source for sugarcane breeding.

Genome-wide identification and expression analysis of the NHX gene family under salt stress in wheat (Triticum aestivum L)

Salt stress affects plant growth and development, resulting in the loss of crop yield across the world, and sodium-proton antiporters (NHXs) are one of the genes known to promote salt tolerance in transgenic plants. In this study, we conducted a comprehensive genome-wide analysis and expression profile of NHX genes in wheat under salinity stress. We identified 30 TaNHX genes in wheat based on the Na+/H+ exchanger domain, with all genes containing an amiloride motif except one, a known for inhibiting Na+ ions in plants. Phylogenetic analysis classified these genes into three classes with subfamilies: 12 were localized in vacuoles, while 18 were in the endoplasmic reticulum and plasma membrane. Promoter analysis revealed stress-related cis-acting elements, indicating their potential role in abiotic stress tolerance. The non-synonymous (Ka)/synonymous (Ks) ratios highlighted that the majority of TaNHX genes experienced robust purifying selection throughout their evolutionary history. Transcriptomis data analysis and qRT-PCR demonstrated distinct expression patterns for TaNHX genes across various tissues when subjected to salt stress. Additionally, we predicted 20 different miRNA candidates targeting the identified TaNHX genes. Protein-protein interaction prediction revealed NHX6's involvement in the SOS1 pathway, while NHX1 gene exhibit proton antiporter activity. Molecular dynamics (MD) simulations were also conducted to examine the interactions of TaNHX1, TaNHX2, and TaNHX3. These results represent a significant advancement in our understanding of the molecular mechanisms governing Na+ transporters. This may also offer promising avenues for future studies aimed at unraveling the intricate details of their biological roles and applications.

Full-Length Transcriptome Analysis of the Halophyte Nitraria sibirica Pall

Background: Nitraria sibirica Pall. is one of the pioneer tree species in saline–alkali areas due to its extreme salt tolerance. However, the lack of information on its genome limits the further exploration of the molecular mechanisms in N. sibirica under salt stress. Methods: In this study, we used single-molecule real-time (SMRT) technology based on the PacBio Iso-Seq platform to obtain transcriptome data from N. sibirica under salt treatment for the first time, which is helpful for our in-depth analysis of the salt tolerance and molecular characteristics of N. sibirica. Results: Our results suggested that a total of 234,508 circular consensus sequences (CCSs) with a mean read length of 2121 bp were obtained from the 19.26 Gb raw data. Furthermore, based on transcript cluster analysis, 93,713 consensus isoforms were obtained, including 92,116 high-quality isoforms. After removing redundant sequences, 49,240 non-redundant transcripts were obtained from high-quality isoforms. A total of 37,261 SSRs, 1816 LncRNAs and 47,314 CDSs, of which 40,160 carried complete ORFs, were obtained. Based on our transcriptome data, we also analyzed the coding genes of H+-PPase, and the results of both bioinformatics and functional analyses indicated that the gene prediction via full-length transcripts obtained by SMRT technology is reliable and effective. In summary, our research data obtained by SMRT technology provides more reliable and accurate information for the further analysis of the regulatory network and molecular mechanism of N. sibirica under salt stress.

Essential role of pyrophosphate homeostasis mediated by the pyrophosphate-dependent phosphofructokinase in Toxoplasma gondii

Many biosynthetic pathways produce pyrophosphate (PPi) as a by-product, which is cytotoxic if accumulated at high levels. Pyrophosphatases play pivotal roles in PPi detoxification by converting PPi to inorganic phosphate. A number of apicomplexan parasites, including Toxoplasma gondii and Cryptosporidium parvum, express a PPi-dependent phosphofructokinase (PPi-PFK) that consumes PPi to power the phosphorylation of fructose-6-phosphate. However, the physiological roles of PPi-PFKs in these organisms are not known. Here, we report that Toxoplasma expresses both ATP- and PPi-dependent phosphofructokinases in the cytoplasm. Nonetheless, only PPi-PFK was indispensable for parasite growth, whereas the deletion of ATP-PFK did not affect parasite proliferation or virulence. The conditional depletion of PPi-PFK completely arrested parasite growth, but it did not affect the ATP level and only modestly reduced the flux of central carbon metabolism. However, PPi-PFK depletion caused a significant increase in cellular PPi and decreased the rates of nascent protein synthesis. The expression of a cytosolic pyrophosphatase in the PPi-PFK depletion mutant reduced its PPi level and increased the protein synthesis rate, therefore partially rescuing its growth. These results suggest that PPi-PFK has a major role in maintaining pyrophosphate homeostasis in T. gondii. This role may allow PPi-PFK to fine-tune the balance of catabolism and anabolism and maximize the utilization efficiency for carbon nutrients derived from host cells, increasing the success of parasitism. Moreover, PPi-PFK is essential for parasite propagation and virulence in vivo but it is not present in human hosts, making it a potential drug target to combat toxoplasmosis.

Different from classic ATP-dependent phosphofructokinases, PPi-PFKs use pyrophosphate consumption to power the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate, the committed step of glycolysis. PPi-PFK is found in diverse organisms including archaea, bacteria, protists and plants. However, half a century after its first discovery, the physiological functions of PPi-PFK are still not well defined. Using the Toxoplasma gondii parasite as a model, here we show that PPi-PFK has a coordinator function to assure matched activities of anabolism and catabolism. This is achieved by maintaining the homeostasis of PPi, which is a byproduct, as well as an inhibitor of many biosynthetic reactions. PPi-PFK hydrolyzes PPi to promote anabolism, meanwhile being a glycolytic enzyme involved in catabolism. As such, it gauges the anabolic and catabolic activities in parasites to maximize the utilization efficiency of acquired nutrients. This work provides important insights to understand the physiological significance of PPi-PFK in Toxoplasma and other organisms.

Plant protein-coding gene families: Their origin and evolution

Steady advances in genome sequencing methods have provided valuable insights into the evolutionary processes of several gene families in plants. At the core of plant biodiversity is an extensive genetic diversity with functional divergence and expansion of genes across gene families, representing unique phenomena. The evolution of gene families underpins the evolutionary history and development of plants and is the subject of this review. We discuss the implications of the molecular evolution of gene families in plants, as well as the potential contributions, challenges, and strategies associated with investigating phenotypic alterations to explain the origin of plants and their tolerance to environmental stresses.

Genome-wide identification, characterization and transcriptional profiling of NHX-type (Na+/H+) antiporters under salinity stress in soybean

This study was aimed at the genome-wide identification, a comprehensive in silico characterization of NHX genes from soybean (Glycine max L.) and their tissue-specific expression under varied levels (0-200 mM NaCl) of salinity stress. A total of nine putative NHX genes were identified from soybean. The phylogenetic analysis confirmed a total of five sub-groups and GmNHXs were distributed in three of them. Bioinformatics analyses confirmed all GmNHXs as ion transporters in nature, and all were localized on the vacuolar membrane. Several cis-acting regulatory elements involved in hormonal signal-responsiveness and abiotic stress including salinity responses were identified in the promoter regions of GmNHXs. Amiloride, which is a known Na⁺/H⁺ exchanger activity inhibitor, binding motifs were observed in all the GmNHXs. Furthermore, the identified GmNHXs were predicted-targets of 75 different miRNA candidates. To gain an insight into the functional divergence of GmNHX transporters, qRT-PCR based gene expression analysis was done in control and salt-treated root, stem and leaf tissues of two contrasting Indian soybean varieties MAUS-47 (tolerant) and Gujosoya-2 (sensitive). The gene up-regulation was tissue-specific and varied amongst the soybean varieties, with higher induction in tolerant variety. Maximum induction was observed in GmNHX2 in root tissues of MAUS-47 at 200 mM NaCl stress. Overall, identified GmNHXs may be explored further as potential gene candidates for soybean improvement.