Biology subjects

Winter, K.

Publications and source records attributed to Winter, K..

6 recordsLinked to original sources

bioRxiv2022

Exploring Xylem Anatomical Adaptations Associated with Crassulacean Acid Metabolism and Hydraulic Capacitance in Clusia Leaves: Lessons for CAM Bioengineering

* Background and AimsMany succulent species are characterised by the presence of crassulacean acid metabolism (CAM) and/or elevated bulk hydraulic capacitance (CFT). Both CAM and elevated CFT substantially reduce the rate at which water moves through transpiring leaves. However, little is known about how these physiological adaptations are coordinated with leaf vascular architecture and xylem anatomy. * MethodsThe genus Clusia contains species spanning the entire C3-CAM continuum, and also is known to have > 5-fold interspecific variation in CFT. We used this highly diverse genus to explore how interspecific variation in vein density and xylem vessel dimensions are coordinated with CAM and CFT. * Key ResultsWe found that constitutive CAM phenotypes were associated with lower vein length per leaf area (VLA) and vein termini density (VTD), compared to C3 or facultative CAM species. However, when vein densities were standardised by leaf depth, this value was higher in CAM than C3 species, which is likely an adaptation to overcome apoplastic hydraulic resistance in deep chlorenchyma tissue. In contrast, CFT did not correlate with any xylem anatomical trait measured, suggesting CAM has a greater impact on leaf hydraulic physiology than CFT. * ConclusionsOur findings strongly suggest that CAM photosynthesis is coordinated with leaf vein densities. The link between CAM and vascular anatomy will be important to consider when attempting to bioengineer CAM into C3 crops.

plant biology↗

bioRxiv2022

Dissecting Succulence: Crassulacean Acid Metabolism and Hydraulic Capacitance are Independent Adaptations in Clusia Leaves

O_LISucculence is found across the world as an adaptation to water-limited niches. The fleshy organs of succulent plants develop via enlarged photosynthetic chlorenchyma and/or achlorophyllous water storage hydrenchyma cells. The precise mechanism by which anatomical traits contribute to drought tolerance is unclear, as the effect of succulence is multifaceted. Large cells are believed to provide space for nocturnal storage of malic acid fixed by crassulacean acid metabolism (CAM), whilst also buffering water potentials by elevating hydraulic capacitance (CFT). Furthermore, the effect of CAM and elevated CFT on growth and water conservation have not been compared, despite the assumption that these adaptations often occur together. C_LIO_LIWe assessed the relationship between succulent anatomical adaptations, CAM and CFT, across the genus Clusia. In addition, we simulated the effects of CAM and CFT on growth and water conservation during drought using the Photo3 model. C_LIO_LIWithin Clusia leaves, CAM and CFT are independent traits: CAM requires large palisade chlorenchyma cells, whereas hydrenchyma tissue governs interspecific differences in CFT. In addition, our model suggests that CAM supersedes CFT as a means to maximise CO2 assimilation and minimise transpiration during drought. C_LIO_LIOur study challenges the assumption that CAM and CFT are mutually dependent traits within succulent leaves. C_LI

plant biology↗

bioRxiv2021

Genetic diversification of persistent Mycobacterium abscessus within Cystic Fibrosis patients

Mycobacterium (M.) abscessus infections in Cystic Fibrosis (CF) patients cause a deterioration of lung function. Treatment of these multidrug-resistant pathogens is associated with severe side-effects, while frequently unsuccessful. Insight on M. abscessus genomic evolvement during chronic lung infection would be beneficial for improving treatment strategies. A longitudinal study enrolling 42 CF patients was performed at a CF center in Berlin, Germany, to elaborate phylogeny and genomic diversification of in-patient M. abscessus. Eleven of the 42 CF patients were infected with M. abscessus. Global human-transmissible M. abscessus cluster strains were isolated from five of these 11 patients. Phylogenetic analysis of 88 genomes from isolates of the 11 patients excluded occurrence of M. abscessus transmission among members of the study group. Genome sequencing and variant analysis of 30 isolates from 11 serial respiratory samples collected over four years from a chronically infected patient demonstrated accumulation of gene mutations. In total, 53 genes exhibiting non-synonymous variations were identified. Enrichment analysis emphasized genes involved in synthesis of glycopeptidolipids, genes from the embABC (arabinosyltransferase) operon, betA (glucose-methanol-choline oxidoreductase) and choD (cholesterol oxidase). Genetic diversity evolved in a variety of virulence- and resistance-associated genes. The strategy of M. abscessus populations in chronic lung infection is not clonal expansion of dominant variants, but to sustain simultaneously a wide range of genetic variants facilitating adaptation of the population to changing living conditions in the lung. Genomic diversification during chronic infection requires increased attention when new control strategies against M. abscessus infections are explored.

genomics↗

bioRxiv2021

Evolution of Crassulacean Acid Metabolism (CAM) as an escape from ecological niche conservatism in Malagasy Bulbophyllum (Orchidaceae)

Introductory paragraphDespite growing evidence that niche shifts are more common in flowering plants than previously thought, still little is known about the key physiological (e.g. photosynthesis) traits underlying such niche shifts. To address this question, we here combine a comprehensively sampled phylogeny for mostly epiphytic Malagasy Bulbophyllum orchids (c. 210 spp.) with climatic niche and carbon isotope-derived photosynthesis data to infer the groups spatial-temporal history and to test the role of Crassulacean Acid Metabolism (CAM), a highly water-use efficient type of photosynthesis, in facilitating niche shifts and diversification. We find that most extant species still retain niche (Central Highland) and photosynthesis (C3) states as likely present in the single mid-Miocene (c. 12.70 Ma) ancestor colonizing Madagascar. However, we also infer a major transition to CAM, linked to a late Miocene (c. 7.36 Ma) invasion of species from the sub-humid highland niche first into the islands humid eastern coastal, and then into the seasonally dry Northwest Sambirano rainforests, yet without significant effect on diversification rates. These findings support the rarely recognized hypothesis that CAM in tropical epiphytes may be selectively advantageous even in high rainfall habitats, rather than presenting a mere adaptation to dry environments or epiphytism per se. Overall, our study qualifies CAM as an evolutionary gateway trait that considerably widened the spatial-ecological amplitude of Madagascars most species-rich orchid genus.

evolutionary biology↗

bioRxiv2018

Altered Gene Regulatory Networks are Associated with the Transition from C3 to Crassulacean Acid Metabolism in Erycina (Oncidiinae: Orchidaceae)

Crassulacean acid metabolism (CAM) photosynthesis is a modification of the core C3 photosynthetic pathway that improves the ability of plants to assimilate carbon in water-limited environments. CAM plants fix CO2 mostly at night, when transpiration rates are low. All of the CAM pathway genes exist in ancestral C3 species, but the timing and magnitude of expression are greatly altered between C3 and CAM species. Understanding these regulatory changes is key to elucidating the mechanism by which CAM evolved from C3. Here we use two closely related species in the Orchidaceae, Erycina pusilla (CAM) and Erycina crista-galli (C3), to conduct comparative transcriptomic analyses across multiple time points. Clustering of genes with expression variation across the diel cycle revealed some canonical CAM pathway genes similarly expressed in both species, regardless of photosynthetic pathway. However, gene network construction indicated that 149 gene families had significant differences in network connectivity and were further explored for these functional enrichments. Genes involved in light sensing and ABA signaling were some of the most differently connected genes between the C3 and CAM Erycina species, in agreement with the contrasting diel patterns of stomatal conductance in C3 and CAM plants. Our results suggest changes to transcriptional cascades are important for the transition from C3 to CAM photosynthesis in Erycina.

plant biology↗

bioRxiv2017

The Potential Role of Genetic Assimilation during Maize Domestication

Domestication research has largely focused on identification of morphological and genetic differences between extant populations of crops and their wild relatives. Little attention has been paid to the potential effects of environment despite substantial known changes in climate from the time of domestication to modern day. Recent research, in which maize and teosinte (i.e., wild maize) were exposed to environments similar to the time of domestication, resulted in a plastic induction of domesticated phenotypes in teosinte and little response to environment in maize. These results suggest that early agriculturalists may have selected for genetic mechanisms that cemented domestication phenotypes initially induced by a plastic response of teosinte to environment, a process known as genetic assimilation. To better understand this phenomenon and the potential role of environment in maize domestication, we examined differential gene expression in maize (Zea mays ssp. mays) and teosinte (Zea mays ssp. parviglumis) between past and present conditions. We identified a gene set of over 2000 loci showing a change in expression across environmental conditions in teosinte and invariance in maize. In fact, overall we observed both greater plasticity in gene expression and more substantial re-wiring of expression networks in teosinte across environments when compared to maize. While these results suggest genetic assimilation played at least some role in domestication, genes showing expression patterns consistent with assimilation are not significantly enriched for previously identified domestication candidates, indicating assimilation did not have a genome-wide effect.

genomics↗