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Summary: Amphicarpy is an unusual trait where two fruit types develop on the same plant: one above and the other belowground. This trait is not found in conventional model species. Therefore, its development and molecular genetics remain under‐studied. Here, we establish the allooctoploid Cardamine chenopodiifolia as an emerging experimental system to study amphicarpy.We characterized C. chenopodiifolia development, focusing on differences in morphology and cell wall histochemistry between above‐ and belowground fruit. We generated a reference transcriptome with PacBio full‐length transcript sequencing and analysed differential gene expression between above‐ and belowground fruit valves.Cardamine chenopodiifolia has two contrasting modes of seed dispersal. The main shoot fails to bolt and initiates floral primordia that grow underground where they self‐pollinate and set seed. By contrast, axillary shoots bolt and develop exploding seed pods aboveground. Morphological differences between aerial explosive fruit and subterranean nonexplosive fruit were reflected in a large number of differentially regulated genes involved in photosynthesis, secondary cell wall formation and defence responses.Tools established in C. chenopodiifolia, such as a reference transcriptome, draft genome assembly and stable plant transformation, pave the way to study amphicarpy and trait evolution via allopolyploidy. [ABSTRACT FROM AUTHOR]

Powdery mildew‐resistant barley (Hordeum vulgare) and Arabidopsis thaliana mlo mutant plants exhibit pleiotropic phenotypes such as the spontaneous formation of callose‐rich cell wall appositions and early leaf chlorosis and necrosis, indicative of premature leaf senescence. The exogenous factors governing the occurrence of these undesired side effects remain poorly understood. Here, we characterised the formation of these symptoms in detail. Ultrastructural analysis revealed that the callose‐rich cell wall depositions spontaneously formed in A. thaliana mlo mutants are indistinguishable from those induced by the bacterial pattern epitope, flagellin 22 (flg22). We further found that increased plant densities during culturing enhance the extent of the leaf senescence syndrome in A. thaliana mlo mutants. Application of a liquid fertiliser rescued the occurrence of leaf chlorosis and necrosis in both A. thaliana and barley mlo mutant plants. Controlled fertilisation experiments uncovered nitrogen as the macronutrient whose deficiency promotes the extent of pleiotropic phenotypes in A. thaliana mlo mutants. Light intensity and temperature had a modulatory impact on the incidence of leaf necrosis in the case of barley mlo mutant plants. Collectively, our data indicate that the development of pleiotropic phenotypes associated with mlo mutants is governed by various exogenous factors. Summary Statement: We analysed the environmental factors that modulate the extent of pleiotropic phenotypes associated with powdery mildew‐resistant mlo mutants in barley and Arabidopsis thaliana. We discovered that in particular plant crowding and the lack of the macronutrient nitrogen promote their occurence. [ABSTRACT FROM AUTHOR]

Finding causal relationships between genotypic and phenotypic variation is a key focus of evolutionary biology, human genetics and plant breeding. To identify genome-wide patterns underlying trait diversity, we assembled a high-quality reference genome of Cardamine hirsuta, a close relative of the model plant Arabidopsis thaliana. We combined comparative genome and transcriptome analyses with the experimental tools available in C. hirsuta to investigate gene function and phenotypic diversification. Our findings highlight the prevalent role of transcription factors and tandem gene duplications in morphological evolution. We identified a specific role for the transcriptional regulators PLETHORA5/7 in shaping leaf diversity and link tandem gene duplication with differential gene expression in the explosive seed pod of C. hirsuta. Our work highlights the value of comparative approaches in genetically tractable species to understand the genetic basis for evolutionary change.

The article is an introduction to the second volume of "Women in Microscopy," which features a collection of papers on various microscopy techniques and technologies. The volume includes contributions on topics such as surface passivation, time-modulated structured illumination, Mesolens imaging, array tomography, and quantification in life sciences microscopy. The article also highlights the implementation of an interdisciplinary bootcamp at UC Berkeley aimed at promoting networking and support for women in microscopy. The bootcamp provides opportunities for undergraduate students to connect with women role models in academia and industry. Other papers in the volume discuss improvements in glass coatings for microscopy, a temporal method for improving localisation precision, mesoscale standing wave imaging, and array tomography in 3D electron microscopy. The volume concludes with a review on microscopy data quantification in the life sciences. Overall, the article showcases the diverse contributions of women in the field of microscopy and highlights the importance of supporting and promoting gender equity in the discipline. [Extracted from the article]

Summary: Arabis alpina is a polycarpic perennial, in which PERPETUAL FLOWERING1 (PEP1) regulates flowering and perennial traits in a vernalization‐dependent manner. Mutagenesis screens of the pep1 mutant established the role of other flowering time regulators in PEP1‐parallel pathways.Here we characterized three allelic enhancers of pep1 (eop002, 085 and 091) which flower early. We mapped the causal mutations and complemented mutants with the identified gene. Using quantitative reverse transcriptase PCR and reporter lines, we determined the protein spatiotemporal expression patterns and localization within the cell. We also characterized its role in Arabidopsis thaliana using CRISPR and in A. alpina by introgressing mutant alleles into a wild‐type background.These mutants carried lesions in an AAA+ ATPase of unknown function, FLOWERING REPRESSOR AAA+ATPase 1 (AaFRAT1). AaFRAT1 was detected in the vasculature of young leaf primordia and the rib zone of flowering shoot apical meristems. At the subcellular level, AaFRAT1 was localized at the interphase between the endoplasmic reticulum and peroxisomes. Introgression lines carrying Aafrat1 alleles required less vernalization to flower and reduced number of vegetative axillary branches. By contrast, A. thaliana CRISPR lines showed weak flowering phenotypes.AaFRAT1 contributes to flowering time regulation and the perennial growth habit of A. alpina. [ABSTRACT FROM AUTHOR]

Background and Aims Seeds are dispersed by explosive coiling of the fruit valves in Cardamine hirsuta. This rapid coiling launches the small seeds on ballistic trajectories to spread over a 2 m radius around the parent plant. The seed surface interacts with both the coiling fruit valve during launch and subsequently with the air during flight. We aim to identify features of the seed surface that may contribute to these interactions by characterizing seed coat differentiation. Methods Differentiation of the outermost seed coat layers from the outer integuments of the ovule involves dramatic cellular changes that we characterize in detail at the light and electron microscopical level including immunofluorescence and immunogold labelling. Key Results We found that the two outer integument (oi) layers of the seed coat contributed differently to the topography of the seed surface in the explosively dispersed seeds of C. hirsuta vs. the related species Arabidopsis thaliana where seed dispersal is non-explosive. The surface of A. thaliana seeds is shaped by the columella and the anticlinal cell walls of the epidermal oi2 layer. In contrast, the surface of C. hirsuta seeds is shaped by a network of prominent ridges formed by the anticlinal walls of asymmetrically thickened cells of the sub-epidermal oi1 layer, especially at the seed margin. Both the oi2 and oi1 cell layers in C. hirsuta seeds are characterized by specialized, pectin-rich cell walls that are deposited asymmetrically in the cell. Conclusions The two outermost seed coat layers in C. hirsuta have distinct properties: the sub-epidermal oi1 layer determines the topography of the seed surface, while the epidermal oi2 layer accumulates mucilage. These properties are influenced by polar deposition of distinct pectin polysaccharides in the cell wall. Although the ridged seed surface formed by oi1 cell walls is associated with ballistic dispersal in C. hirsuta , it is not restricted to explosively dispersed seeds in the Brassicaceae. [ABSTRACT FROM AUTHOR]