Biology subjects

Wulff, N.

Publications and source records attributed to Wulff, N..

4 recordsLinked to original sources

bioRxiv2025

Chromosome-Scale Genome Assembly of Australian Finger Lime and Resequencing Reveal the Hidden Diversity of Oceanian Citrus

Oceanian citrus species, including wild taxa native to Australia and Papua New Guinea, form a genetically distinct clade within the Citrus L. (1753) genus. These species remain largely underexplored, despite their adaptation to diverse environments and relevance for citrus improvement. To support their use in breeding and evolutionary studies, we generated a high-quality, Chromosome-scale genome assembly of an Australian finger lime accession (SRA 1002), a natural interspecific hybrid. The genome was assembled using long-read sequencing, optical mapping, and a high-density genetic map, resulting in nine pseudomolecules covering over 97% of the genome. Using this reference, we analyzed whole-genome resequencing data from 132 accessions representing the diversity of Asian and Oceanian citrus. Variant calling across the dataset produced a high-resolution catalogue of single nucleotide polymorphisms (SNPs) and derived database of SNP fully discriminant of 20 Citrus species (DSNPs), enabling detailed exploration of inter- and intra-specific diversity. The data reveal a strong population structure within the group with clear heterozygosity variation between ancestral species and admixed accessions, reflecting their complex evolutionary history and hybridization patterns. This study provides the first integrated genomic framework for Oceanian citrus diversity, offering essential tools for downstream applications in citrus breeding, conservation, and evolutionary genomics. The resources generated lay the groundwork for future association studies and the targeted introgression of beneficial traits into cultivated citrus.

plant biology↗

bioRxiv2023

Mechanistic insight into substrate specificity of plant glucosinolate transporters

Plants depend on transport processes for correct allocation of specialized metabolites. This is important for optimal defense, avoidance of autotoxicity, connecting compartmented biosynthetic modules and more. Transport of a wide variety of specialized metabolites is mediated by transporters from the Nitrate and Peptide transporter Family (NPF), which belongs to the Major Facilitator Superfamily (MFS). However, the mechanism by which NPF members recognize and transport specialized metabolites remains unknown. Here we mutate eight residues to reciprocally swap the substrate-preference of two closely related glucosinolate transporters (GTRs). Seven of these residues assemble in a ring-like structure in all conformations of the transporters. We labeled the ring-like structure a selectivity filter and based on docking studies, we propose that the interaction between the selectivity filter and the glucosinolate side chain determines whether a given glucosinolate is recognized as a substrate. Besides partly explaining the distinct substrate preference of GTR1 (NPF2.10) and GTR3 (NPF2.9), this study proposes fundamental principles of substrate recognition in the NPF and establishes the GTR subclade as a novel model system for studying structure function relationships in the NPF.

molecular biology↗

bioRxiv2021

ABA homeostasis and long-distance translocation is redundantly regulated by ABCG ABA importers

The effects of abscisic acid (ABA) on plant growth, development and response to the environment depend on local ABA concentrations. Here, we exploited a genome-scale amiRNA screen, targeting the Arabidopsis transportome, to show that ABA homeostasis is regulated by two previously unknown ABA transporters. ABCG17 and ABCG18 are localized to the plasma membranes of leaf mesophyll and stem cortex cells to redundantly promote ABA import, leading to conjugated inactive ABA sinks, thus restricting stomatal closure. ABCG17 and ABCG18 double knockdown revealed that the transporters encoded by these genes not only limit stomatal aperture size, conductance and transpiration while increasing water-use efficiency but also control ABA translocation from the shoot to the root to regulate lateral root emergence. The proposed ABCG17- and ABCG18-dependent ABA glucosyl ester shoot sink mechanism is restrained under abiotic stress conditions to further activate the ABA responses.

plant biology↗

bioRxiv2019

An Optimized Screen Reduces the Number of GA Transporters and provides Insights into NPF Substrate Determinants

Based on recent in vitro data, a relatively large number of the plant Nitrate transporter 1/Peptide transporter Family (NPF) proteins has been suggested to function as gibberellic acid (GA) transporters. Most GA transporting NPF proteins also appear to transport other structurally unrelated phytohormones or metabolites. Several of the GAs used in previous in vitro assays are membrane permeable weak organic acids whose movement across membranes are influenced by the pH-sensitive ion-trap mechanism. Moreover, a large proportion of in vitro GA transport activities have been demonstrated indirectly via long-term yeast-based GA-dependent growth assays that are limited to detecting transport of bioactive GAs. Thus, there is a need for an optimized transport assay for identifying and characterizing GA transport. Here, we develop an improved transport assay in Xenopus laevis oocytes wherein we directly measure movement of six different GAs across oocyte membranes over short time. We show that membrane permeability of GAs in oocytes can be predicted based on number of oxygen atoms and that several GAs do not diffuse over membranes regardless of changes in pH values. In addition, we show that small changes in internal cellular pH can result in strongly altered distribution of membrane permeable phytohormones. This prompts caution when interpreting heterologous transport activities. We use our transport assay to screen all Arabidopsis thaliana NPF proteins for transport activity towards six GAs (two membrane permeable and four non-permeable). The results presented here, significantly reduce the number of bona fide NPF GA transporters in Arabidopsis and narrow the activity to fewer subclades within the family. Furthermore, to gain first insight into the molecular determinants of substrate specificities towards organic molecules transported in the NPF, we charted all surface exposed amino acid residues in the substrate-binding cavity and correlated them to GA transport. This analysis identified distinct residues within the substrate-binding cavity that are shared between GA transporting NPF proteins; the potential roles of these residues in determining substrate specificity are discussed.

biochemistry↗