Gene expression evolution in pattern-triggered immunity within Arabidopsis thaliana and across Brassicaceae species.

Plants recognize surrounding microbes by sensing microbe-associated molecular patterns (MAMPs) to activate pattern-triggered immunity (PTI). Despite their significance for microbial control, the evolution of PTI responses remains largely uncharacterized. Here, by employing comparative transcriptomics of six Arabidopsis thaliana accessions and three additional Brassicaceae species to investigate PTI responses, we identified a set of genes that commonly respond to the MAMP flg22 and genes that exhibit species-specific expression signatures. Variation in flg22-triggered transcriptome responses across Brassicaceae species was incongruent with their phylogeny, while expression changes were strongly conserved within A. thaliana. We found the enrichment of WRKY transcription factor binding sites in the 5'-regulatory regions of conserved and species-specific responsive genes, linking the emergence of WRKY-binding sites with the evolution of gene expression patterns during PTI. Our findings advance our understanding of the evolution of the transcriptome during biotic stress.

Loss of MYB34 Transcription Factor Supports the Backward Evolution of Indole Glucosinolate Biosynthesis in a Subclade of the Camelineae Tribe and Releases the Feedback Loop in This Pathway in Arabidopsis.

Glucosinolates are specialized defensive metabolites characteristic of the Brassicales order. Among them, aliphatic and indolic glucosinolates (IGs) are usually highly abundant in species from the Brassicaceae family. The exceptions this trend are species representing a subclade of the Camelineae tribe, including Capsella and Camelina genera, which have reduced capacity to produce and metabolize IGs. Our study addresses the contribution of specific glucosinolate-related myeloblastosis (MYB) transcription factors to this unprecedented backward evolution of IG biosynthesis. To this end, we performed phylogenomic and functional studies of respective MYB proteins. The obtained results revealed weakened conservation of glucosinolate-related MYB transcription factors, including loss of functional MYB34 protein, in the investigated species. We showed that the introduction of functional MYB34 from Arabidopsis thaliana partially restores IG biosynthesis in Capsella rubella, indicating that the loss of this transcription factor contributes to the backward evolution of this metabolic pathway. Finally, we performed an analysis of the impact of particular myb mutations on the feedback loop in IG biosynthesis, which drives auxin overproduction, metabolic dysregulation and strong growth retardation caused by mutations in IG biosynthetic genes. This uncovered the unique function of MYB34 among IG-related MYBs in this feedback regulation and consequently in IG conservation in Brassicaceae plants.

The role of CYP71A12 monooxygenase in pathogen-triggered tryptophan metabolism and Arabidopsis immunity.

Effective defense of Arabidopsis against filamentous pathogens requires two mechanisms, both of which involve biosynthesis of tryptophan (Trp)-derived metabolites. Extracellular resistance involves products of PEN2-dependent metabolism of indole glucosinolates (IGs). Restriction of further fungal growth requires PAD3-dependent camalexin and other, as yet uncharacterized, indolics. This study focuses on the function of CYP71A12 monooxygenase in pathogen-triggered Trp metabolism, including the biosynthesis of indole-3-carboxylic acid (ICA). Moreover, to investigate the contribution of CYP71A12 and its products to Arabidopsis immunity, we analyzed infection phenotypes of multiple mutant lines combining pen2 with pad3, cyp71A12, cyp71A13 or cyp82C2. Metabolite profiling of cyp71A12 lines revealed a reduction in ICA accumulation. Additionally, analysis of mutant plants showed that low amounts of ICA can form during an immune response by CYP71B6/AAO1-dependent metabolism of indole acetonitrile, but not via IG hydrolysis. Infection assays with Plectosphaerella cucumerina and Colletotrichum tropicale, two pathogens with different lifestyles, revealed cyp71A12-, cyp71A13- and cyp82C2-associated defects associated with Arabidopsis immunity. Our results indicate that CYP71A12, but not CYP71A13, is the major enzyme responsible for the accumulation of ICA in Arabidopsis in response to pathogen ingression. We also show that both enzymes are key players in the resistance of Arabidopsis against selected filamentous pathogens after they invade.

How to explore what is hidden? A review of techniques for vascular tissue expression profile analysis.

The evolution of plants to efficiently transport water and assimilates over long distances is a major evolutionary success that facilitated their growth and colonization of land. Vascular tissues, namely xylem and phloem, are characterized by high specialization, cell heterogeneity, and diverse cell components. During differentiation and maturation, these tissues undergo an irreversible sequence of events, leading to complete protoplast degradation in xylem or partial degradation in phloem, enabling their undisturbed conductive function. Due to the unique nature of vascular tissue, and the poorly understood processes involved in xylem and phloem development, studying the molecular basis of tissue differentiation is challenging. In this review, we focus on methods crucial for gene expression research in conductive tissues, emphasizing the importance of initial anatomical analysis and appropriate material selection. We trace the expansion of molecular techniques in vascular gene expression studies and discuss the application of single-cell RNA sequencing, a high-throughput technique that has revolutionized transcriptomic analysis. We explore how single-cell RNA sequencing will enhance our knowledge of gene expression in conductive tissues.

Brain-derived neurotrophic factor serum levels in genetically isolated populations: gender-specific association with anxiety disorder subtypes but not with anxiety levels or Val66Met polymorphism.

Anxiety disorders (ADs) are disabling chronic disorders with exaggerated behavioral response to threats. This study was aimed at testing the hypothesis that ADs may be associated with reduced neurotrophic activity, particularly of Brain-derived neurotrophic factor (BDNF), and determining possible effects of genetics on serum BDNF concentrations. In 672 adult subjects from six isolated villages in North-Eastern Italy with high inbreeding, we determined serum BDNF levels and identified subjects with different ADs subtypes such as Social and Specific Phobias (PHSOC, PHSP), Generalized Anxiety Disorder (GAD), and Panic Disorder (PAD). Analysis of the population as a whole or individual village showed no significant correlation between serum BDNF levels and Val66Met polymorphism and no association with anxiety levels. Stratification of subjects highlighted a significant decrease in serum BDNF in females with GAD and males with PHSP. This study indicates low heritability and absence of any impact of the Val66Met polymorphism on circulating concentrations of BDNF. Our results show that BDNF is not a general biomarker of anxiety but serum BDNF levels correlate in a gender-specific manner with ADs subtypes.