Biology subjects

Hannah, M. A.

Publications and source records attributed to Hannah, M. A..

4 recordsLinked to original sources

bioRxiv2023

Analysis of Arabidopsis venosa4-0 supports the role of VENOSA4 in dNTP homeostasis

An imbalance in the deoxyribonucleoside triphosphate (dNTP) pool caused by an increase or decrease in the levels of any of the four dNTPs leads to increased DNA mutations, overloading DNA repair mechanisms. The human protein SAMHD1 (Sterile alpha motif and histidine-aspartate domain containing protein 1) functions as a dNTPase to maintain the balance of the dNTP pool, as well as in DNA repair. In eukaryotes, the limiting step in de novo dNTP synthesis is catalyzed by RIBONUCLEOTIDE REDUCTASE (RNR), which consists of two R1 and two R2 subunits. In Arabidopsis, RNR1 is encoded by CRINKLED LEAVES 8 (CLS8) and RNR2 by three paralogous genes, including TSO2 (TSO MEANING UGLY IN CHINESE 2). In plants, the de novo biosynthesis of purines occurs within the chloroplast, and DOV1 (DIFFERENTIAL DEVELOPMENT OF VASCULAR ASSOCIATED CELLS 1) catalyzes the first step of this pathway. Here, to explore the role of VENOSA4 (VEN4), the most likely Arabidopsis ortholog of human SAMHD1, we studied the ven4-0 mutant. The mutant leaf phenotype caused by the ven4-0 point mutation was stronger than those of T-DNA insertional ven4 mutations. Structural predictions suggested that the E249L amino acid substitution in the mutated VEN4-0 protein rigidifies its 3D structure compared to wild-type VEN4. The morphological phenotypes of the ven4, cls8, and dov1 single mutants were similar, and those of the ven4 tso2 and ven4 dov1 double mutants were synergistic. The ven4-0 mutant had reduced levels of four amino acids related to dNTP biosynthesis, including glutamine and glycine, which are precursors in the de novo purine biosynthesis pathway. Finally, despite its annotation in some databases, At5g40290, a paralog of VEN4, is likely a pseudogene. These observations support the previously proposed role of VEN4 in dNTP metabolism. Our results reveal a high degree of cross-kingdom functional conservation between VEN4 and SAMHD1 in dNTP homeostasis.

plant biology↗

bioRxiv2022

Mutation of Arabidopsis SME1 and Sm core assembly improves oxidative stress resilience

Alternative splicing is a key posttranscriptional gene regulatory process, acting in diverse adaptive and basal plant processes. Splicing of precursor-messenger RNA (pre-mRNA) is catalyzed by a dynamic ribonucleoprotein complex, designated the spliceosome. In a suppressor screen, we identified a nonsense mutation in the Sm protein SME1 to alleviate photorespiratory H2O2-dependent cell death in catalase deficient plants. Similar attenuation of cell death was observed upon chemical inhibition of the spliceosome, suggesting pre-mRNA splicing inhibition to be responsible for the observed cell death alleviation. Furthermore, the sme1-2 mutants showed increased tolerance to the reactive oxygen species inducing herbicide methyl viologen. Both an mRNA-seq and shotgun proteomic analysis in sme1-2 mutants displayed a constitutive molecular stress response, together with extensive alterations in pre-mRNA splicing of transcripts encoding metabolic enzymes and RNA binding proteins, even under unstressed conditions. Using SME1 as a bait to identify protein interactors, we provide experimental evidence for almost 50 homologs of mammalian spliceosome-associated protein to reside in the Arabidopsis thaliana spliceosome complexes and propose roles in pre-mRNA splicing for four uncharacterized plant proteins. Furthermore, like in sme1-2, a mutant in the Sm core assembly protein ICLN resulted in a decreased sensitivity to methyl viologen. Taken together, these data show that both a perturbed Sm core composition and assembly results in the activation of a defense response and enhanced resilience to oxidative stress.

plant biology↗

bioRxiv2022

Overexpression of the WAPO-A1 gene increases the number of spikelets per spike in bread wheat

Two homoeologous QTLs for number of spikelets per spike (SPS) were mapped on chromosomes 7AL and 7BL using two wheat MAGIC populations. Sets of lines contrasting for the QTL on 7AL were developed which allowed for the validation and fine mapping of the 7AL QTL and for the identification of a previously described candidate gene, WHEAT ORTHOLOG OF APO1 (WAPO1). Using transgenic overexpression in both a low and a high SPS line, we provide a functional validation for the role of this gene in determining SPS also in hexaploid wheat. We show that the expression levels of this gene positively correlate with SPS in multiple MAGIC founder lines under field conditions as well as in transgenic lines grown in the greenhouse. This work highlights the potential use of WAPO1 in hexaploid wheat for further yield increases. The impact of WAPO1 and SPS on yield depends on other genetic and environmental factors, hence, will require a finely balanced expression level to avoid the development of detrimental pleiotropic phenotypes.

plant biology↗

bioRxiv2021

Wheat EARLY FLOWERING3 is a dawn-expressed circadian oscillator component that regulates heading date

Using an eight-parent Multiparent Advanced Generation Inter-Cross (MAGIC) population we investigated how variation at circadian clock-associated genes contributes to the regulation of heading date in UK and European winter wheat varieties. We identified homoeologues of EARLY FLOWERING 3 (ELF3) as candidates for the Earliness per se (Eps) D1 and B1 loci in field conditions. We confirmed that a SNP within the coding region of TaELF3-B1 is a candidate polymorphism underlying the Eps-B1 locus. We found that a reported deletion at the Eps-D1 locus encompassing TaELF3-D1, is instead a novel allele that lies within an introgression region containing an inversion relative to the Chinese Spring D genome. Using T. turgidum cv. Kronos carrying loss of function alleles of TtELF3 we show that ELF3 does regulate heading by demonstrating that the loss of a single ELF3 homoeologue was sufficient to alter heading date. These studies demonstrated that ELF3 forms part of the circadian oscillator but loss of all homoeologues was required to affect circadian rhythms. Similarly, loss of functional LUX ARRHYTHMO (LUX) in T. aestivum, an orthologue of a protein partner of Arabidopsis ELF3, severely disrupted circadian rhythms. ELF3 and LUX transcripts are not co-expressed at dusk suggesting the structure of the wheat circadian oscillator might differ to that of Arabidopsis. Our demonstration that alteration to ELF3 homoeologues can affect heading date separate from effects on the circadian oscillator suggests a role for ELF3 in cereal photoperiodic responses that could be selected for, without pleiotropic deleterious alterations to circadian rhythms.

plant biology↗