Biology subjects

Batista, R. A.

Publications and source records attributed to Batista, R. A..

3 recordsLinked to original sources

bioRxiv2024

Modifiers of genetic dominance at the Arabidopsis self-incompatibility locus retain proto-miRNA features and act through non-canonical gene silencing pathways

Self-incompatibility in flowering plants is a common mechanism that prevents self-fertilization and promotes outcrossing. In Brassicaceae, the self-incompatibility locus is highly diverse, with many alleles arranged in a complex dominance hierarchy and exhibiting monoallelic expression in heterozygote individuals. Monoallelic expression of the pollen self-incompatibility gene is achieved through the action of sRNA precursors that resemble miRNAs, although the underlying molecular mechanisms remain elusive. Here, we engineered Arabidopsis thaliana lines expressing components of the Arabidopsis halleri self-incompatibility system, and used a reverse genetics approach to pinpoint the pathways underlying the function of these sRNA precursors. We showed that they trigger a robust decrease in transcript abundance of the recessive self-incompatibility genes, but not through the canonical transcriptional or post-transcriptional gene silencing pathways. Furthermore, we observed that single sRNA precursors are typically processed into hundreds of sRNA molecules with a variety of sizes, abundance levels and ARGONAUTE loading preferences. Our results suggest that these seemingly arbitrary processing characteristics are essential for establishing the self-incompatibility dominance hierarchy, as they enable a single sRNA precursor from a dominant allele to effectively repress multiple recessive alleles, thus providing a unique example of how small RNAs mediate gene silencing within a highly complex regulatory network. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/591913v3_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@b32c02org.highwire.dtl.DTLVardef@10e65d3org.highwire.dtl.DTLVardef@3f14b3org.highwire.dtl.DTLVardef@1682d57_HPS_FORMAT_FIGEXP M_FIG C_FIG

plant biology↗

bioRxiv2023

The diallelic self-incompatibility system in Oleaceae is controlled by a hemizygous genomic region expressing a gibberellin pathway gene

Sexual reproduction in flowering plants is commonly controlled by self-incompatibility (SI) systems that are either homomorphic (and typically governed by large numbers of distinct allelic specificities), or heteromorphic (and then typically governed by only two allelic specificities). The SI system of the Oleaceae family is a striking exception to this rule and represents an evolutionary conundrum, with the long-term maintenance of only two allelic specificities, but often in the complete absence of morphological differentiation between them. To elucidate the genomic architecture and molecular bases of this highly unusual SI system, we obtained chromosome-scale genome assemblies of Phillyrea angustifolia individuals belonging to the two SI specificities and connected them to a genetic map. Comparison of the S-locus region revealed a segregating 543-kb indel specific to one of the two specificities, suggesting a hemizygous genetic architecture. Only one of the predicted genes in this indel is conserved with the olive tree Olea europaea, where we also confirmed the existence of a segregating hemizygous indel. We demonstrated full association between presence/absence of this gene and the SI groups phenotypically assessed across six distantly related Oleaceae species. This gene is predicted to be involved in catabolism of the Gibberellic Acid (GA) hormone, and experimental manipulation of GA levels in developing buds modified the male and female SI responses in an S-allele-specific manner. Thus, our results provide a unique example of a reproductive system where a single conserved gibberellin-related gene in a 500-700kb hemizygous indel underlies the long-term maintenance of two groups of reproductive compatibility.

evolutionary biology↗

bioRxiv2017

Auxin regulates endosperm cellularization in Arabidopsis

The endosperm is an ephemeral tissue that nourishes the developing embryo, similar to the placenta in mammals. In most angiosperms endosperm development starts as a syncytium, where nuclear divisions are not followed by cytokinesis. The timing of endosperm cellularization largely varies between species and the event triggering this transition remains unknown. Here we show that increased auxin biosynthesis in the endosperm prevents its cellularization, leading to seed arrest. Auxin-overproducing seeds phenocopy paternal-excess triploid seeds derived from hybridizations of diploid maternal plants with tetraploid fathers. Concurrently, auxin-related genes are strongly overexpressed in triploid seeds, correlating with increased auxin activity. Reducing auxin biosynthesis and signaling reestablishes endosperm cellularization in triploid seeds and restores their viability, highlighting a causal role of increased auxin in preventing endosperm cellularization. We propose that auxin determines the time of endosperm cellularization and thereby uncovered a central role of auxin in establishing hybridization barriers in plants.

plant biology↗