Melissa L Harris’s research while affiliated with University of Alabama at Birmingham and other places

The relative rates of sexual versus asexual reproduction influence the partitioning of genetic diversity within and among populations. During range expansions, asexual reproduction often facilitates colonization and establishment. The arrival of the green alga Avrainvillea lacerata has caused shifts in habitat structure and community assemblages since its discovery in 1981 offshore of Oʻahu, Hawai‘i. Field observations suggest this species is spreading via vegetative reproduction. To characterize the reproductive system of A. lacerata in Hawai‘i, we developed seven microsatellite loci and genotyped 321 blades collected between 2018 and 2023 from three intertidal sites at Maunalua Bay and ʻEwa Beach. We observed one to four alleles at multiple loci, suggesting A. lacerata is tetraploid. Each site was characterized by high genotypic richness ( R > 0.8). However, clonal rates were also high, suggesting the vegetative spread of A. lacerata plays a significant role. The importance of clonal reproduction for the persistence of A. lacerata in Hawai‘i is consistent with the ecological data collected for this species and observations of other abundant macroalgal invaders in Hawai‘i and other regions of the world. These data demonstrate the necessity for implementing appropriate population genetic methods and provide insights into the biology of this alga that will contribute to future studies on effective management strategies incorporating its reproductive system. This study represents one of the few that investigate green algal population genetic patterns and contributes to our understanding of algal reproductive system evolution.

The relative rates of sexual versus asexual reproduction influence the partitioning of genetic diversity within and among populations. During range expansions, uniparental reproduction often facilitates colonization and establishment. The arrival of the green alga Avrainvillea lacerata has caused shifts in habitat structure and community assemblages since its discovery in 1981 offshore of west Oahu, Hawaii. Field observations suggest this species is spreading via vegetative reproduction. To characterize the reproductive system of A. lacerata in Hawaii, we developed seven microsatellite loci and genotyped 321 blades collected between 2018 and 2023 from two intertidal sites at Maunalua Bay and 'Ewa Beach. We found one to four alleles at multiple loci, suggesting A. lacerata is tetraploid. Each site was characterized by high genotypic richness (R > 0.8). However, clonal rates were also high at both sites, suggesting vegetative spread of A. lacerata plays a significant role. The importance of clonal reproduction for the persistence of A. lacerata in Hawaii is consistent with the ecological data collected for this species, and observations of other abundant macroalgal invaders in Hawaii and other regions of the world. These data demonstrate the necessity for implementing appropriate population genetic methods and provide insights into the biology of this alga that will contribute to future studies on effective management strategies incorporating its reproductive system. This study represents one of the few investigating green algal population genetic patterns and contributes to our understanding of algal reproductive system evolution.

Hair graying, also known as canities or achromotrichia, is a natural phenomenon associated with aging and is influenced by external factors such as stress, environmental toxicants, and radiation exposure. Understanding the mechanisms underlying hair graying is an ideal approach for developing interventions to prevent or reverse age-related changes in regenerative tissues. Hair graying induced by ionizing radiation (γ-rays or X-rays) has emerged as a valuable experimental model to investigate the molecular pathways involved in this process. In this review, we examine the existing evidence on radiation-induced hair graying, with a particular focus on the potential role of radiation-induced cellular senescence. We explore the current understanding of hair graying in aging, delve into the underlying mechanisms, and highlight the unique advantages of using ionizing-irradiation–induced hair graying as a research model. By elucidating the molecular pathways involved, we aim to deepen our understanding of hair graying and potentially identify novel therapeutic targets to address this age-related phenotypic change.

Cyclic adenosine monophosphate (cAMP) signaling is a well-established regulator of melanin synthesis. Two distinct cAMP signaling pathways, the transmembrane adenylyl cyclase (tmAC) pathway, activated primarily by the melanocortin 1 receptor (MC1R), and the soluble adenylyl cyclase (sAC) pathway, affect melanin synthesis. The sAC pathway affects melanin synthesis by regulating melanosomal pH, and the MC1R pathway affects melanin synthesis by regulating gene expression and post-translational modifications. However, whether MC1R genotype affects melanosomal pH is poorly understood. We now demonstrate that loss of function MC1R does not affect melanosomal pH. Thus, sAC signaling appears to be the only cAMP signaling pathway that regulates melanosomal pH. We also addressed whether MC1R genotype affects sAC-dependent regulation of melanin synthesis. Even though sAC loss of function in wild type human melanocytes stimulates melanin synthesis, sAC loss of function has no effect on melanin synthesis in MC1R non-functional human and mouse melanocytes or skin and hair melanin in (e/e) mice. Interestingly, activation of tmACs, which increases epidermal eumelanin synthesis in e/e mice, leads to enhanced production of eumelanin in sAC knockout mice relative to sAC wild type mice. Thus, MC1R- and sAC-dependent cAMP signaling pathways define distinct mechanisms that regulate melanosomal pH and pigmentation.