Biology subjects

Chow, H. T.

Publications and source records attributed to Chow, H. T..

4 recordsLinked to original sources

bioRxiv2023

RNA-directed DNA Methylation is required for seed development in outbreeding species

In plants, de novo DNA methylation is guided by 24-nt short interfering (si)RNAs in a process called RNA-directed DNA methylation (RdDM). Primarily targeted at transposons, RdDM causes transcriptional silencing and can indirectly influence expression of neighboring genes. During reproduction, a small number of siRNA loci are dramatically upregulated in the maternally-derived seed coat, suggesting that RdDM might have a special function during reproduction. However, the developmental consequence of RdDM has been difficult to dissect because disruption of RdDM does not result in overt phenotypes in Arabidopsis thaliana, where the pathway has been most thoroughly studied. In contrast, Brassica rapa mutants lacking RdDM have a severe seed production defect, which is determined by the maternal sporophytic genotype. To explore the factors that underlie the different phenotypes of these species, we produced RdDM mutations in three additional members of the Brassicaceae family: Camelina sativa, Capsella rubella, and Capsella grandiflora. Among these three species, only mutations in the obligate outcrosser, C. grandiflora, displayed a seed production defect similar to Brassica rapa mutants, suggesting that mating system is a key determinant for reproductive phenotypes in RdDM mutants.

plant biology↗

bioRxiv2022

Mapping a mutation causing pale yellow petals in Brassica rapa

Petal color is an important trait for both ornamental purposes and also for attracting pollinators. Here, we report a mutation of Brassica rapa R-o-18 with pale yellow petals that we retrieved from an EMS population and named whiter shade of pale (wsp). Phenotypic segregation ratio of an F2 mapping population indicates the phenotype is controlled by a single recessive gene. Mapping data from the whole genome sequencing coupled with allele frequency analysis suggests the mutation is located in a [~]2 Mbp interval on chromosome 2. The interval contains a putative esterase/lipase/thioesterase protein previously demonstrated to account for floral color in B. rapa. We demonstrate that wsp carries a G to A missense mutation causing an aspartate to asparagine substitution within the putative lysophospholipid acyltransferase domain.

plant biology↗

bioRxiv2022

A novel CLAVATA1 mutation causes multilocularity in Brassica rapa

Locules are the seed-bearing structure of fruits. Multiple locules are associated with increased fruit size and seed set, and therefore control of locule number is an important agronomic trait. Locule number is controlled in part by the CLAVATA-WUSCHEL pathway. Disruption of either the CLAVATA1 receptor-like kinase or its ligand CLAVATA3 can cause larger floral meristems and an increased number of locules. In an EMS mutagenized population of Brassica rapa, we identified a mutant allele that raises the number of locules from 4 to a range of from 6 to 8. Linkage mapping and genetic analysis support that the mutant phenotype is due to a missense mutation in a CLAVATA 1 (CLV1) homolog. In addition to increased locule number, brclv1 individuals fail to terminate their floral meristems, resulting in internal gynoecia that negatively impact seed production.

plant biology↗

bioRxiv2021

Ovule siRNAs methylate and silence protein-coding genes in trans

24-nt small interfering siRNAs maintain asymmetric DNA methylation at thousands of euchromatic transposable elements in plant genomes in a process call RNA-directed DNA Methylation (RdDM). RdDM is dispensable for growth and development in Arabidopsis, but is required for reproduction in other plant species, such as Brassica rapa. 24-nt siRNAs are particularly abundant in maternal reproductive tissue, due largely to overwhelming expression from a small number of loci in the ovule and developing seed coat, termed siren loci. Recently it was shown that abundantly expressed 24-nt siRNAs produced in the tapetal tissue of anthers can methylate male meiocyte genes in trans (Long et al., 2021). Here we show that a similar process takes place in female tissue. siRNAs are produced from gene fragments embedded in some siren loci, and these siRNAs can trigger methylation in trans at related protein-coding genes. This trans-methylation is associated with silencing of some target genes and may be responsible for seed abortion in RdDM mutants. Furthermore, we demonstrate that a consensus sequence in at least two families of DNA transposons is associated with abundant siren expression, most likely through recruitment of the CLSY3 putative chromatin remodeller. This research describes a new mechanism whereby RdDM influences gene expression and sheds light on the role of RdDM during plant reproduction.

plant biology↗