Biology subjects

Jakobson, L.

Publications and source records attributed to Jakobson, L..

3 recordsLinked to original sources

bioRxiv2023

Phylogenetic analysis of ABCE genes across the plant kingdom

ATP-BINDING CASSETTE SUBFAMILY E MEMBER (ABCE) proteins are one of the most conserved proteins across eukaryotes and archaea. Yeast and the vast majority of animals possess a single ABCE gene encoding the vital ABCE1 protein. We retrieved ABCE gene sequences of 76 plant species from public genome databases and analyzed them with the reference to Arabidopsis thaliana ABCE2 gene (AtABCE2). Over half of the studied plant species possess two or more ABCE genes. There can be as many as eight ABCE genes in a plant species. This suggest that ABCE genes in plants can be classified as a low-copy gene family, rather than a single-copy gene family. Plant ABCE proteins showed overall high sequence conservation, sharing at least 78% of amino acid sequence identity with AtABCE2. The phylogenetic trees of full-length ABCE amino acid and CDS sequences demonstrated that Brassicaceae and Poaceae families have independently undergone lineage-specific split of the ancestral ABCE gene. Other plant species have gained ABCE gene copies through more recent duplication events. Deeper analysis of AtABCE2 and its paralogue AtABCE1 from 1135 Arabidopsis thaliana ecotypes revealed 4 and 35 non-synonymous SNPs, respectively. The lower natural variation in AtABCE2 compared to AtABCE1 is in consistence with its crucial role for plant viability. Overall, while the sequence of the ABCE protein family is highly conserved in the plant kingdom, many plants have evolved to have more than one copy of this essential translational factor. Significance statementIn most eukaryotes there is a single ABCE protein, which is involved in many vital processes in cells. However, less is known about ABCEs specifically in plants. Here we show that while the sequence of ABCE proteins is highly conserved in plants, they have evolved to often have multiple copies of this essential translational factor. By studying 76 species from the entire plant kingdom, we observed as many as eight ABCE genes being present at a time, although most species have less. Some ABCE copies appeared earlier than others and were found in multiple species. Thus, our findings indicate that ABCE genes in plants are not a single-copy gene family and should instead be re-classified as a low-copy gene family.

evolutionary biology↗

bioRxiv2022

ALMT-independent guard cell R-type anion currents

Plant transpiration is controlled by stomata, with S- and R-type anion channels playing key roles in guard cell action. Arabidopsis mutants lacking the ALMT12/QUAC1 R-type anion channel function in guard cells show only a partial reduction in R-type channel currents. To identify the molecular nature of the remaining R-type anion channel population, patch clamp studies were performed. This R-type current fraction in the almt12 mutant exhibited the same voltage dependence, susceptibility to ATP block and lacked a chloride permeability as the wildtype. Therefore, we asked whether the R-type anion currents in the ALMT12/QUAC1-free mutant are caused by additional ALMT isoforms. In wildtype guard cells ALMT12, ALMT13 and ALMT14 transcripts were detected, whereas only ALMT13 was found expressed in the almt12 mutant. Substantial R-type anion currents still remained active in the almt12/13 and almt12/14 double mutants as well as the almt12/13/14 triple mutant. This situation, supported by transpiration measurements, suggests that, with the exception of ALMT12, channel species other than ALMTs carry the guard cell R-type anion currents.

plant biology↗

bioRxiv2019

The role of strigolactones in regulation of stomatal conductance and plant-pathogen interactions in Arabidopsis thaliana

Strigolactones are a group of phytohormones that control shoot branching in Arabidopsis thaliana. However, in recent years they have been shown to affect many other plant processes. We previously showed that the strigolactone perception mutant more axillary branches 2 (max2) has increased susceptibility to plant pathogenic bacteria as a result of more open stomata as well as alterations in hormonal signalling. Here we show that both, strigolactone biosynthesis- (max3 and max4), and perception mutants (max2 and dwarf14) are significantly more sensitive to Pseudomonas syringae DC3000. Moreover, in response to P. syringae infection, high levels of SA accumulated in max2 and this mutant was ozone sensitive. To search for the mechanisms that could explain pathogen- and ozone sensitivity we performed gene expression analysis and several different assays that explore the function of guard cells and regulation of guard cell signalling.\n\nTreatments with GR24 (a strigolactone analogue) resulted in very modest changes in defence-related gene expression. In contrast, guard cell function was clearly impaired in max2 and depending on the assay used, also in max3, max4 and d14 mutants. Moreover, stomatal responses to stimuli that cause stomatal closure in wild-type plants (darkness, high CO2 and ABA) were analysed in the strigolactone mutants. In darkness both strigolactone biosynthesis and perception mutants showed reduced stomatal closure, whereas the response to high CO2 was impaired only in max2 and d14. The response to ABA was not impaired in any of the mutants. To position the role of MAX2 in the guard cell signalling network, max2 was crossed with mutants defective in ABA biosynthesis (aba2), in guard cell ABA signalling (ost1) and a scaffold protein required for proper ion channel activity (ghr1). The stomatal conductance of double mutants was consistently higher than the corresponding single mutants, suggesting that MAX2 acts in a signalling pathway that functions in parallel to the well characterized guard cell ABA signalling pathway. We propose that the impaired defence responses of max2 is related to more open stomata that allows increased entry of bacteria or air pollutants like ozone. Furthermore, as MAX2 appears to act in a specific branch of guard cell signalling (related to CO2 signalling), this protein could be one of the elusive components that allow guard cells to distinguish between different environmental conditions.

plant biology↗