Cluster of Excellence on Plant Sciences

Petrichor – a strong scent released from desiccated soil upon rewetting – is a mixture of volatile organic compounds (VOCs) that impact atmospheric chemistry and originates from the abiotic desorption of stored compounds and the de novo microbial production. The aridity gradient of the Negev Desert soils provides a particularly suitable system for studying petrichor emissions due to their distinctive and well-studied microbial communities (e.g., Actinobacteria and Cyanobacteria) but similar physical properties that control VOC physical evaporation, and absence of plant material as confounding sources of VOCs. While the chemical and microbial origins of petrichor are relatively well described, the controlling factors of its emission remain unclear. This study investigated the influences of desiccation dynamics on petrichor emissions and microbial succession in soils from an aridity gradient of the Negev Desert in Israel. Soil cores were subjected to three sequential rain events followed by contrasting desiccation regimes (long drought, rapid desiccation and slow desiccation) in a realistic climate simulation. Their VOC emissions and microbial metatranscriptomics were studied at five time points, including three upon rewetting and two during slow desiccation. The results showed that VOCs were produced during soil drying, with compound-specific release patterns occurring either during desiccation or upon rehydration. Despite having a common biosynthetic pathway, monoterpenoid and sesquiterpenoid emissions exhibited distinct temporal dynamics, suggesting different underlying physical control or microbial activity. The abundances and chemical diversity of petrichor decreased with increasing aridity, closely following the decline in microbial diversity. The microbial communities varied among rewetting scenarios and exhibited clear temporal succession during slow desiccation, likely regulating petrichor emissions through microbial activation. Greater community dispersion at 24 hours after rewetting indicated rapid and heterogeneous microbial reactivation, potentially contributing to increased variability and reduced predictability of early petrichor emissions. These findings highlighted the importance of desiccation rate in controlling petrichor emissions in desert ecosystems. Further field measurements and functional microbial analyses will be essential to understand how changing desiccation regimes will reshape petrichor emissions and the microbial communities in desert ecosystems.

<title>Abstract</title> <italic>Daphne tangutica</italic> Maxim is a perennial evergreen shrub with significant ornamental and economic value, but its low fruit set rate restricts its development and utilization. To improve breeding and conservation strategies, there is an urgent need to clarify its gametophyte development process and the causes of abortion. Using wild populations as materials, paraffin sectioning and microscopic observation were employed to systematically conduct cytological observations and descriptions of megasporogenesis and microsporogenesis, male gametophyte development, the type of anther wall development, and embryo sac formation, among others. The microspores of <italic>D. tangutica</italic> are tetrahedral in shape, and mature pollen is mainly of the bicellular type; the anther wall shows basic-type development. The megaspore develops into a Polygonum-type and ultimately forms a Polygonum-type embryo sac, indicating that the female gametophyte functions are basically intact. During the late stage of pollen development, residual material appears in the tapetum (forming continuous or semi-continuous band-like structures along the inner wall of the anther), accompanied by partial anther abortion and the production of non-viable pollen, resulting in a reduced number of fertile pollen grains. Environmental stresses at high altitude, such as low temperatures, strong winds, a short growing season, and restricted pollinator activity, may exacerbate the occurrence of developmental asynchrony and pollen abortion. This study systematically elucidates for the first time the developmental processes of the megaspores and male and female gametophytes of <italic>D. tangutica</italic> , revealing that pollen abortion associated with asynchronous male development and delayed tapetum degradation is one of the main factors leading to low fruit set, whereas the female gametophyte is generally normal. The research findings provide a theoretical basis for embryological studies of <italic>Thymelaeaceae</italic> plants and offer support for determining appropriate pollination timing, improving propagation and breeding schemes, and further investigating the mechanisms of abortion.

Hemicelluloses are a group of plant cell wall polysaccharides characterized by their high structural complexity. These glycans are part of an intricate composite polymer network that contribute to the mechanical strength and flexibility of plant cell walls. Hemicellulose structural and functional diversity is further enhanced by the presence of chemical modifications, such as O-acetylation, altering the polysaccharide's physicochemical properties and the overall functionality. Plant-derived hemicellulose glycans hold great promise for a range of biotechnological applications in a bioeconomy including biomaterials and pharmaceuticals. Synthetic biology approaches have the potential to produce hemicellulose polymers in microbial factories replicating the biosynthetic pathways observed in plants. In this study, we successfully reconstructed in the yeast Yarrowia lipolytica the biosynthesis of two hemicellulose backbone structures i.e., β-glucomannan (GM) and β-glucan, by the expression of glycosyltransferases of diverse plant origins. Oligosaccharide mass profiling combined with compositional and glycosidic linkage analysis confirmed the production of hemicellulose structures analogous to those found in the original plant systems. Furthermore, the additional expression of plant hemicellulose-specific O-acetyltransferases resulted in the biosynthesis of O-acetylated GM and O-acetylated glucan polymers, expanding the repertoire of hemicellulose structures produced in this yeast. These findings demonstrate the feasibility of generating not only compositionally diverse plant-like hemicellulose backbone polymers in microbial systems, but also more structurally complex O-acetylated variants beyond what is found in nature. The use of Y. lipolytica as a biofactory for designer glycans expands the potential of microbial glycoengineering and provides a platform for sustainable production of functionalized polysaccharides with tailored physicochemical properties optimized for specific biotechnological applications.

We hypothesized that B-GATA family transcription factors have important roles in growth regulation in moss. We analyzed B-GATA family transcription factor mutants from Physcomitrium patens and Arabidopsis thaliana to assess growth, gene expression, and cytokinin-related processes under varying nitrogen conditions. We found that nitrogen-dependent growth and transcriptional regulation are strongly impaired in mutants from Physcomitrium and Arabidopsis. We detected altered cytokinin homeostasis or signaling in the mutants, linking hormonal imbalance to growth and transcription defects. We demonstrated a conserved, critical role of B-GATAs in plant nitrogen-responsive growth. Results suggest that B-GATAs influence nitrogen-regulated transcription downstream from cytokinin, supporting an ancient, evolutionarily conserved mechanism connecting nutrient signaling to growth. We provided experimental evidence for the long-speculated but as-yet not demonstrated role of GATA transcription factors in nitrogen-dependent growth in land plants.

SummaryIncreasing frequencies of severe summer droughts and plant diversity loss disrupt ecosystem functioning and stability of European grasslands. Understanding how these factors interact with pathogens is crucial.We investigated the effects of plant diversity and repeated summer drought on soil‐borne parasites within a grassland biodiversity experiment. The experiment included plant communities ranging from 1 to 60 species, with a sub‐experiment simulating annual droughts for 6 wk in summer over 9 yr. One year after the final drought period, we analyzed the diversity and community composition of two parasitic protistan taxa with many plant‐pathogenic members, Oomycota (Stramenopila) and Phytomyxea (Rhizaria), as well as protistan consumers in the Cercozoa (Rhizaria) using amplicon sequencing.Both Oomycota and Cercozoa, including Phytomyxea, responded to plant species richness and drought, but not uniformly. Plant species‐specific Oomycota were enriched under drought, while Phytomyxea and cercozoan consumers exhibited shifts in both enriched and reduced operational taxonomic units. No mitigating effect of plant diversity against the effects of drought was observed.Our findings suggest that repeated summer droughts weaken plant defense against protistan plant parasites, causing long‐lasting soil legacy effects across plant communities varying in diversity and community composition, potentially threatening ecosystem stability and functioning under future climate conditions.

Abstract Beneficial root-associated microbes can enhance plant resilience by complementing aspects of host immunity. The fungal root endophyte Serendipita indica ( Si ) is known to promote plant growth and confer broad stress tolerance. To assess how natural host genetic variation influences Si -mediated protection, we screened 47 Arabidopsis thaliana accessions for susceptibility to the fungal pathogen Bipolaris sorokiniana ( Bs ) with and without Si colonization. All accessions benefited from Si , indicating that endophyte-mediated disease mitigation occurs broadly across diverse host genotypes. A focused comparison of two genetically and geographically proximate Swedish accessions, T510 and T530, which displayed the most divergent protection scores, revealed substantial differences in Bs susceptibility. Transcriptome profiling under bi- and tripartite colonization showed conserved defense responses in both accessions. Bs infection downregulated growth- and development-related genes, consistent with a growth–immunity trade-off, with T530 exhibiting higher Bs colonization and a stronger transcriptional response than T510. Co-colonization with Si effectively suppressed pathogen growth and disease symptoms in both accessions. Comparative genomic and transcriptomic analyses identified four immune receptor genes, including the TIR-NLR ISI , present in T510 but absent in T530. An isi T-DNA insertion mutant phenocopied the heightened Bs susceptibility of T530, confirming that ISI contributes to root immunity, while Si -mediated protection remained intact despite increased pathogen susceptibility. Together, these findings demonstrate that fungal endophytes can mitigate the functional consequences of natural immune variation and enhance the resilience of genetically diverse plant populations. Highlights S. indica confers broad protection against B. sorokiniana largely independent of host genotype or pathogen susceptibility. The TIR-NLR immune receptor ISI contributes to root immunity but is not essential for S. indica -mediated protection. Beneficial endophytes can mitigate natural immune variation effects and support overall plant health.

Abstract The pre-anthesis embryonic inflorescence greening (PEIG) is a distinctive developmental feature in the members of the Triticeae such as barley, wheat and rye. In barley ( Hordeum vulgare L.), floral survival and fertility are major determinants of grain yield, yet the physiological processes supporting early inflorescence development remain poorly understood. Here, we investigated PEIG, a light-dependent chlorophyll accumulation occurring while immature inflorescences are still enclosed by leaf sheaths, and its role in overall inflorescence development. Using chlorophyll autofluorescence imaging and chlorophyll quantification, we found that PEIG in barley initiates at a surprisingly early developmental stage, when developing spikes are still enclosed by leaf sheaths. PEIG first appears in the central rachis and then progressively spreads to the spikelet primordia and other floral organs. Using a non-destructive dark treatment method designed for preventing light exposure to developing inflorescences, we further demonstrated that the inhibition of PEIG does not affect floral initiation but significantly reduces floral survival and pollen viability, particularly in the tip region of the inflorescence, indicating a critical role of light mediated PEIG in floral fate. Finally, analysis of natural variation for PEIG revealed a strong positive correlation between PEIG and floral survival. Our findings establish PEIG as an underappreciated hidden trait that supports floral viability and reproductive success, with implications to enhance grain yield potential in cereals.

Abstract The first generations of most clone breeding programs do not allow multi‐environment trials due to the lack of sufficient reproductive organs. We integrated the phenotypic records of such an early timepoint, called the A clone stage in potato ( Solanum tuberosum L.) breeding, into a genomic prediction framework and analyzed (i) if different relationship information can enhance the accuracy of the breeding values from such unreplicated trials, and (ii) whether a weighted combination of these enhanced breeding values with predicted breeding values calculated through genomic prediction can further improve accuracy. Compared to the breeding values derived without considering any relationship information among the clones, enhanced breeding values achieved a higher accuracy for 7–14 traits, depending on the relationship matrix used (multispectral, genetic, pedigree, or a combination). Combining these enhanced breeding values with predicted values from genomic prediction via a heritability index resulted in a weak increase of accuracy (0.5%) for five traits. However, a grid search to find the optimal combination of weights revealed more traits (8–12) with a higher mean increase of accuracy (0.5%–3.8%). Our findings show that the accuracies of unreplicated clones can be increased with easy‐to‐collect multispectral and pedigree data. The magnitude of this accuracy increase was negatively correlated with the per plot heritabilities, which makes this approach effective for lowly heritable traits. We see potential for this approach in the early stages of potato breeding programs, like the seedling or single hill stage, where the exact assessment of complex traits is impossible due to low heritability.

High-density lipoprotein (HDL) metabolism depends on several key factors, including ATP-binding cassette (ABC) transporters such as ABCA1 and ABCG1. These transporters are essential for maintaining cholesterol homeostasis by mediating the efflux of cellular lipids and promoting HDL formation and maturation. Dysfunction in these pathways compromises HDL biogenesis, leading to lipid accumulation in macrophages and peripheral cells. Together with oxidized low-density lipoproteins (LDLs), these alterations promote foam cell formation, atherosclerotic plaque development, and the progression of cardiovascular and metabolic diseases. Oxidative stress plays a central role in disturbing lipid balance and impairing ABC transporter activity. Unlike previous reviews that have mainly summarized mechanisms of oxidative regulation, this work integrates recent molecular findings to propose a unifying framework in which oxidative stress sequentially disrupts ABCA1 and ABCG1 function, thereby altering HDL metabolism. Moreover, it highlights emerging pharmacological strategies aimed at restoring cholesterol homeostasis and mitigating oxidative damage, contributing to the prevention of cardiovascular and metabolic disorders.