Gunn, H. | Search bioRxiv

bioRxiv2025

In-depth phenotyping reveals unexpected floral trait variation in Mimulus cardinalis across a range-wide latitudinal gradient

Background & AimsPollinators play a crucial role in the evolution and diversification of flowering plants. Intraspecific variation in floral traits occurs frequently and likely reflects variable biotic and abiotic selection pressures. The hummingbird-pollinated monkeyflower Mimulus cardinalis occurs across western North America, where geographic mosaics of selection have likely influenced its natural history, due to this wide species range. Processes driving early stages of divergence and speciation remain poorly understood, though theory predicts that trait divergence will be most likely at range edges. Within M. cardinalis, which is usually red-flowered and hummingbird-pollinated, two independent shifts to yellow flowers have occurred at the northern and southern range edges, including a population found on Cedros Island, off the coast of Baja California, Mexico. MethodsThis study characterises the local climatic variables of five accessions of M. cardinalis derived from locations across a latitudinal geographic gradient. Highly integrative methods in metabolomics and morphological analyses were used to characterise a suite of pollinator-relevant floral traits across the range of M. cardinalis species variation. We use transcriptomics and whole genome sequencing to study underlying genetic variation in two yellow-coloured, range-edge accessions. Key ResultsThis study uncovers high levels of variation in morphology, nectar properties, pigmentation and scent profile across geographically diverse Mimulus cardinalis accessions, in addition to profiling how these accessions are perceived by potential pollinators. We find high levels of phenotypic variation across M. cardinalis, particularly in the biochemistry of pigment and scent, where inflorescences that appear to be the same shade of red have completely different anthocyanin profiles. Floral trait-underlying genetic differences between different M. cardinalis lines were also investigated, revealing potential mechanisms underlying floral diversification. ConclusionsThis work highlights the importance of interplay between floral trait diversification, pollinator perception and climate. This work also highlights the importance of considering suites of floral traits in a quantitative fashion when studying intraspecific variation in relation to species range. This study also provides genetic insight into changes in these traits and provides many future directions to study the early stages of pollinator-mediated trait differentiation across a species range.

plant biology↗

bioRxiv2019

The right microbial stimulus can direct innate immune effector cells to specific organ sites to clear pathology

Recent developments in understanding how the functional phenotype of the innate immune system is programmed has led to paradigm-shifting views on immunomodulation. These advances have overturned two long-held dogmas: only adaptive immunity confers immunological memory and innate immunity lacks specificity. This work describes the novel observation that innate immune effector cells can be recruited to specific tissues of the body where pathology is present by using a microbial-based immune stimulus that consists of an inactivated pathogen that typically resides or causes infection in that target tissue site. We demonstrate this principle using experimental models of cancer and infection for which different subcutaneously delivered microbial-based treatments were shown to induce the recruitment of immune effector cells to specific diseased organs. Amelioration of disease in a given organ niche was dependent on matching the correct microbial stimulus for the affected organ site but was independent of the nature of the pathology. This observation intriguingly suggests that the immune system, upon pathogen recognition, tends to direct its resources to the compartment in which the pathogen has previously been encountered and would be the most likely source of infection. Importantly, this phenomenon provides a novel means to therapeutically target innate immune effector cells to sites of specific disease localization to potentially treat a wide spectrum of pathologies, including cancer, infection, and chronic inflammatory disorders.\n\nAUTHOR SUMMARYVaccines that target adaptive immune memory have revolutionized medicine. This study describes a novel strategy that works as a modified innate immune \"vaccine\" that exploits the trained response of innate immune effector cells to clear pathology in a specific tissue site. Unlike memory of the adaptive immune system, which functions like a lock and key, innate immune memory is more akin to a reflex response - like experienced muscle or neural cells that are changed by a stimulus to respond more efficiently upon re-exposure. This change in behavior through experience is the definition of learning. Our study suggests that this innate immune learning occurs at different levels. Emergency hematopoiesis trains new innate immune cells in the bone marrow to respond quickly and effectively to a non-specific threat; whereas, pathogen-specific training occurs at sites where cells making up the immunologic niche have had interactions with a particular pathogen and have been trained to respond more robustly to it upon re-presentation in the context of a danger signal. The speed with which new immune cells are trained in the bone marrow in response to an imminent microbial threat and their subsequent recruitment to the target organ site where that microbe typically resides suggests there are ways the immune system communicates to coordinate this rapid response that are yet to be fully delineated. These findings provide a novel highly proficient way to harness the potent effector functions of the innate immune system to address a wide range of immune-based diseases.

immunology↗