Izabela Pawłowicz

Background: The flowering and tuberization are controlled by common determinants that mediate the regulation of both processes. Among transcription regulators involved in light-dependent aspects of growth and development are B-box zinc finger proteins. To gain a better understanding of the StBBX24 role in flowering and tuber formation, we aimed to investigate the regulatory network of StBBX24 in apical shoot parts at different stages of development and in stolons at the hook stage of tuber formation in StBBX24 -silenced and -overexpressed lines using RNA-seq. In addition, we intended to identify StBBX24-targeted genes specific to the light-dark cycle and potentially involved in potato reproduction by performing CHIP-seq. Results: The genome-wide analysis of StBBX24 binding sites identified numerous light- and dark-specific targets, among them those participating in the induction of flowering and floral development. RNA-seq analysis of the apical shoot parts of StBBX24 -silenced and -overexpressed lines revealed substantial modifications in the expression of genes functioning in the flowering process. Furthermore, hook-stage stolons transcriptomics of the transgenic lines revealed that the StBBX24 protein also affects the tuberization process through alteration of the expression of genes participating in stolon-to-tuber transition. Conclusions: Altogether, these data reveal that StBBX24 is involved in potato flowering repression and impedes the formation of tubers. Our results provided a more comprehensive understanding of the molecular basis of potato reproduction and the participation of the StBBX24 protein in this process.

Background: We present the first long-read genome assembly and annotation for Festuca glaucescens , a member of a genus characterized by polyploidy, large genome sizes, and a high content of repetitive sequences. Fescues are important forage and turf grasses in temperate regions, valued for their resilience to abiotic stress. Though, the allotetraploid F. glaucescens is particularly notable for its drought tolerance, yet its genomic architecture has remained largely unexplored. Results: The haploid assembly spans 5.52 Gb, with > 98% gene space completeness as assessed by BUSCO. Repetitive elements comprise ~ 77% of the genome, dominated by Gypsy and Copia LTR retrotransposons. We predicted 72,385 protein-coding genes, the majority of which are supported by transcriptomic and homology-based evidence. While some contig-level fragmentation persists, the assembly successfully captures the gene-rich, repeat-dense landscape of this complex polyploid genome. Conclusions: This is the first annotated reference genome for a Festuca species, offering a foundational resource for functional genomics, comparative studies, and forage grass improvement.

Brassica napus L. is one of the world’s most important oilseed crops. Blackleg disease is a serious, yield-limiting factor in the cultivation of oilseed rape. Genetic resistance is primarily conferred by major resistance (R) genes. In this study, we analyzed the expression of the blackleg resistance genes Rlm3, Rlm4, and Rlm7 following inoculation with the Leptosphaeria maculans isolate using the RT-qPCR method. Additionally, we demonstrated and assessed their interactions. The results showed that, while Rlm3 was weakly induced, Rlm4 and Rlm7 displayed variable expression post-inoculation. The correlation between phenotypic and genotypic similarity was low. This suggests that transcriptional responses do not fully explain resistance patterns. Furthermore, significant main effects of the analyzed genes, as well as two- and three-way interactions, were indicated. These results support current knowledge of gene-mediated resistance to blackleg in oilseed rape.

Triacylglycerol is a key lipid compound involved in the maintaining homeostasis of both membrane lipids and free fatty acids in plant cells under adverse environmental conditions. However, its role in the process of lipid remodeling has not been fully recognized, especially in monocots, including grass species. For our study, two closely related introgression forms of Lolium multiflorum (Italian ryegrass) and Festuca arundinacea (tall fescue), distinct in their level of drought tolerance, were selected as plant models to study rearrangements in plant lipidome under water deficit and further re-watering. The low drought tolerant (LDT) form revealed an elevated level of cellular membrane damage accompanied by an increased content of polyunsaturated free fatty acids and triacylglycerol under water deficit, compared with the high drought tolerant (HDT) form. However, the LDT introgression form demonstrated also the ability to regenerate its membranes after stress cessation. The obtained results clearly indicated that accumulation of triacylglycerol under advanced drought in the LDT form could serve as a cellular protective mechanism against over-accumulation of toxic polyunsaturated free fatty acids and other lipid intermediates. Furthermore, accumulation of triacylglycerol under drought conditions could serve also as a storage of substrates required for further regeneration of membranes after stress cessation. The rearrangements in triacylglycerol metabolism were supported by the up-regulation of several genes, involved in a biosynthesis of triacylglycerol. With respect to this process, diacylglicerol O-acyltransferase DGAT2 seems to play the most important role in the analyzed grasses.

Fusarium species are common plant pathogens that cause several important diseases. They produce a wide range of secondary metabolites, among which mycotoxins and extracellular cell wall-degrading enzymes (CWDEs) contribute to weakening and invading the host plant successfully. Two species of Fusarium isolated from peas were monitored for their expression profile of three cell wall-degrading enzyme coding genes upon culturing with extracts from resistant (Sokolik) and susceptible (Santana) pea cultivars. The extracts from Santana induced a sudden increase in the gene expression, whereas Sokolik elicited a reduced expression. The coherent observation was that the biochemical profile of the host plant plays a major role in regulating the fungal gene expression. In order to uncover the fungal characteristics in planta, both pea cultivars were infected with two strains each of F. proliferatum and F. oxysporum on the 30th day of growth. The enzyme activity assays from both roots and rhizosphere indicated that more enzymes were used for degrading the cell wall of the resistant host compared to the susceptible host. The most commonly produced enzymes were cellulase, β-glucosidase, xylanase, pectinase and lipase, where the pathogen selectively degraded the components of both the primary and secondary cell walls. The levels of beauvericin accumulated in the infected roots of both cultivars were also monitored. There was a difference between the levels of beauvericin accumulated in both the cultivars, where the susceptible cultivar had more beauvericin than the resistant one, showing that the plants susceptible to the pathogen were also susceptible to the toxin accumulation.

Though winter-hardiness is a complex trait, freezing tolerance was proved to be its main component. Species from temperate regions acquire tolerance to freezing in a process of cold acclimation, which is associated with the exposure of plants to low but non-freezing temperatures. However, mechanisms of cold acclimation in Lolium-Festuca grasses, important for forage production in Europe, have not been fully recognized. Thus, two L. multiflorum/F. arundinacea introgression forms with distinct freezing tolerance were used herein as models in the comprehensive research to dissect these mechanisms in that group of plants. The work was focused on: (i) analysis of cellular membranes’ integrity; (ii) analysis of plant photosynthetic capacity (chlorophyll fluorescence; gas exchange; gene expression, protein accumulation, and activity of selected enzymes of the Calvin cycle); (iii) analysis of plant antioxidant capacity (reactive oxygen species generation; gene expression, protein accumulation, and activity of selected enzymes); and (iv) analysis of Cor14b accumulation, under cold acclimation. The more freezing tolerant introgression form revealed a higher integrity of membranes, an ability to cold acclimate its photosynthetic apparatus and higher water use efficiency after three weeks of cold acclimation, as well as a higher capacity of the antioxidant system and a lower content of reactive oxygen species in low temperature.

Lolium multiflorum/Festuca arundinacea introgression forms have been proved several times to be good models to identify key components of grass metabolism involved in the mechanisms of tolerance to water deficit. Here, for the first time, a relationship between photosynthetic and antioxidant capacities with respect to drought tolerance of these forms was analyzed in detail. Two closely related L. multiflorum/F. arundinacea introgression forms distinct in their ability to re-grow after cessation of prolonged water deficit in the field were selected and subjected to short-term drought in pots to dissect precisely mechanisms of drought tolerance in this group of plants. The studies revealed that the form with higher drought tolerance was characterized by earlier and higher accumulation of abscisic acid, more stable cellular membranes, and more balanced reactive oxygen species metabolism associated with a higher capacity of the antioxidant system under drought conditions. On the other hand, both introgression forms revealed the same levels of stomatal conductance, CO₂ assimilation, and consequently, intrinsic water use efficiency under drought and recovery conditions. However, simultaneous higher adjustment of the Calvin cycle to water deficit and reduced CO₂ availability, with respect to the accumulation and activity of plastid fructose-1,6-bisphosphate aldolase, were clearly visible in the form with higher drought tolerance.

Impact of photosynthetic and antioxidant capacities on drought tolerance of two closely related forage grasses, Festuca arundinacea and Festuca glaucescens, was deciphered. Within each species, two genotypes distinct in drought tolerance were subjected to a short-term drought, followed by a subsequent re-watering. The studies were focused on: (i) analysis of plant physiological performance, including: water uptake, abscisic acid (ABA) content, membrane integrity, gas exchange, and relative water content in leaf tissue; (ii) analysis of plant photosynthetic capacity (chlorophyll fluorescence; gene expression, protein accumulation, and activity of selected enzymes of the Calvin cycle); and (iii) analysis of plant antioxidant capacity (reactive oxygen species (ROS) generation; gene expression, protein accumulation and activity of selected enzymes). Though, F. arundinacea and F. glaucescens revealed different strategies in water uptake, and partially also in ABA signaling, their physiological reactions to drought and further re-watering, were similar. On the other hand, performance of the Calvin cycle and antioxidant system differed between the analyzed species under drought and re-watering periods. A stable efficiency of the Calvin cycle in F. arundinacea was crucial to maintain a balanced network of ROS/redox signaling, and consequently drought tolerance. The antioxidant capacity influenced mostly tolerance to stress in F. glaucescens.

Background: Photosynthesis is among the primary processes affected by drought and its disturbances result with the reduction of growth, reactive oxygen species (ROS) overproduction, and alterations in antioxidant system activity. Our study was performed on two closely related forage grasses: Festuca arundinacea and F. glaucescens. Two genotypes within each species significantly differing with the potential of drought resistance: high drought resistant (HDR) and low drought resistant (LDR), were used. The research involved: (i) the analysis of gene expression at transcript and protein levels for the selected enzymes of Calvin cycle (fructose-1,6-bisphosphate aldolase (pFBA), phosphoglycerate kinase (PGK) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH)) and (ii) the activity of pFBA, as a protein marker of the Calvin cycle, (iii) the analysis of gene expression at protein level for the selected antioxidant enzymes (glutathione reductase (GR), glutathione peroxidase (GPX), L-ascorbate peroxidase (APX), catalase (CAT), and superoxide dismutase (SOD)), (iv) the measurements of physiological parameters describing a plant’s physiological status under control, drought and re-watering conditions (relative water content (RWC), electrolyte leakage (EL), lipid peroxidation, chlorophyll fluorescence, gas exchange, and ROS level).Results: Our analysis clearly showed that physiological reactions to water deficit were similar in both HDR and both LDR genotypes of Festuca arundinacea and F. glaucescens but the species revealed significant differences in the potential to tolerate tissue dehydration, what was correlated with distinct expression of the Calvin cycle enzymes under drought stress.Conclusions: The maintenance of stable efficiency of dark phase of photosynthesis seems to be crucial for drought tolerance and recovery in F. glaucescnes, whereas acquisition of drought tolerance in F. arundinacea and F. glaucescens does not involve marked changes at the protein level in the enzymatic antioxidant system.