Biology subjects

Laine, S.

Publications and source records attributed to Laine, S..

3 recordsLinked to original sources

bioRxiv2026

Biochemical, structural, and functional characterization of the Nocardia asteroides dihydrofolate reductase: a primary target of anti-nocardiosis treatment

Nocardiosis is a human infectious disease caused by several species of Nocardia and primarily affecting the skin, lungs and central nervous system. The first line treatment is based on cotrimoxazole, combining trimethoprim and sulfamethoxazole. These two drugs target respectively the dihydrofolate synthase (DHFR) and the dihydropteroate synthase (DHPS) involved in the essential folate synthesis pathway. The occurrence of drug resistance to these two drugs is however frequent. While the molecular mechanisms of trimethoprim resistance are well documented in other bacteria, they remain poorly explored and documented in Nocardia. This is partly because few biochemical structural or genetic studies have been conducted on DHFR from this genus. In this study, we report the biochemical and structural characterization of DHFR from Nocardia asteroides (DHFRNad). We show that overexpression of DHFRNad in N. asteroides confers strong resistance to trimethoprim. We recombinantly expressed and purified active DHFRNad and determined its inhibition constant for trimethoprim. We solved the crystal structure of DHFRNad bound to trimethoprim at high resolution. Further, biochemical studies of mutant DHFR variants pinpointed the role of important residues for trimethoprim binding and drug-resistance. HighlightsFirst biochemical and structural characterization of Nocardia asteroides DHFR. Overexpression of DHFRNad induces high-level trimethoprim resistance in N. asteroides. Crystal structure of DHFRNad reveals key residues for trimethoprim binding. Mutagenesis confirms residues critical for trimethoprim susceptibility. IC50 data confirm strong DHFRNad inhibition by trimethoprim and methotrexate

microbiology↗

bioRxiv2024

Natural variation suggests new mechanisms for bract development in Arabidopsis, desynchronising bract suppression from the floral transition

Plant development may be viewed as a sequence of tightly orchestrated events in space and time. The coordination of developmental stages gives rise to various organs, such as leaves or flowers. For instance, in Arabidopsis thaliana, leaf/bract development ceases once the first flower emerges. Unravelling the mechanisms of this regulation is, therefore, key for understanding how developmental programs are coordinated during the floral transition. In this study, we take advantage of a previously overlooked natural variation that desynchronizes bract repression from the initiation of the first flowers. We found that prolonged bract formation after the floral transition depends on complex genetic interactions, involving at least four loci. Surprisingly, none of these loci contained the floral identity genes previously implicated in bract repression, suggesting that other genes are involved in the synchronisation of bract and flower programs. Furthermore, although ectopic bracts in inflorescences have been interpreted as a prolonged vegetative state, time-series transcriptomics and curve registration revealed a more complex scenario whereby many genes desynchronize in terms of expression between these developmental programs. As a consequence, transcriptional differences peak at the floral transition when bract development is prolonged, affecting a wide variety of biological processes not necessarily associated with vegetative state. A transient increase in transcriptome divergence has been proposed to account for morphological variation between species in animals and plants under the "inverse hourglass" model. Our results suggest that such a model could also explain the sensitivity of certain developmental transitions to phenotypic variation within species, as reported here for the floral transition.

plant biology↗

bioRxiv2018

A network of transcriptional repressors mediates auxin response specificity

INTRODUCTORY PARAGRAPHThe regulation of signalling capacity plays a pivotal role in setting developmental patterns in both plants and animals (1). The hormone auxin is a key signal for plant growth and development that acts through the AUXIN RESPONSE FACTOR (ARF) transcription factors (2). A subset of these ARFs comprises transcriptional activators of target genes in response to auxin, and are essential for regulating auxin signalling throughout the plant lifecycle (3). While ARF activators show tissue-specific expression patterns, it is unknown how their expression patterns are established. Chromatin modifications and accessibility studies revealed the chromatin of loci encoding ARF activators is constitutively open for transcription. Using a high-throughput yeast one-hybrid (Y1H) approach, we discovered a network of transcriptional regulators of ARF activator genes from Arabidopsis thaliana. Expression analyses demonstrated that the majority of these regulators act as repressors of ARF transcription in planta. Our observations support a scenario where the default configuration of open chromatin enables a network of transcriptional repressors to shape the expression pattern of ARF activators and provide specificity in auxin signalling output throughout development.

plant biology↗