The inadvertent introduction and rapid spread of chestnut blight (caused by Cryphonectria parasitica (Murr.) Barr) in the early 20th century resulted in the demise of American chestnut (Castanea dentata (Marsh.) Borkh.; Fagaceae) as a major component of forest canopies and had negative impacts on eastern forest communities. Research efforts over the last century have documented the persistence of occasional trees and root crown/stump sprouts throughout much of the species' historic range providing the basis for ongoing breeding of blight-resistant stock and restoration efforts. Unfortunately, it remains unclear how much of the historic range remains climatically suitable for remnant trees that may harbor unique genetic variation for successful reintroduction efforts. Here we investigate whether the southwestern portion of the historical range remains environmentally suitable for undiscovered remnant populations of C. dentata using environmental niche modeling. We also use stage-structured matrix projection models to investigate the potential demographic future of C. dentata in W Tennessee, N Mississippi, SW Kentucky, and NW Alabama based upon observations of American chestnut in these areas over the last several decades. We found that suitable habitat associated with higher elevations and areas of high forest canopy cover occurs throughout much of the southwestern portion of the historical range and that populations of American chestnut in these areas are predicted to drastically decline over the next ~100-200 years without conservation interventions to mitigate the negative consequences of chestnut blight.

The large, long-lived, epiphytic bromeliad Tillandsia utriculata is currently listed as state-endangered in Florida due to significant population reduction from predation by an invasive weevil, Metamasius callizona. We have developed a novel demographic model of a population of T. utriculata in Myakka River State Park (MRSP) in Sarasota, Florida using a stage-structured matrix model. Analysis of the model revealed conditions for population viability over a variety of parameter scenarios. Model analysis showed that without weevil predation the minimum germination rate required for population viability is low (4–16%), and that given a viable population at structural equilibrium we would expect to find <1% of the population in flower or post-flowering each year and, at most, about 10% of rosettes with longest leaf length (LLL) > 15 cm in flower or post-flowering each year. Additionally, the model presented here provides a basis for further analyses which explore specific conservation strategies.

Cytokinesis is an essential component of cellular development in filamentous fungi. The process parallels that of cell division in animal cells in requiring assembly and constriction of a contractile actomyosin ring (CAR) in the cell periphery. However, the process differs from that in animals by involving the simultaneous construction of a chitin‐rich cross wall termed a septum, which separates semi‐independent compartments of the fungal hypha. Through randomized mutations, we have generated a temperature‐sensitive mutant defective in septum formation, designated strain RCH59. Mendelian crossing confirmed that the temperature sensitive phenotype results from a single locus mutation. Next Generation Whole Genome Sequencing identified a mutation that is located in gene AN4566 encoding the homolog of Saccharomyces cerevisiae's Hof1. The mutation in Aspergillus nidulans’ version of Hof1 (AnHof1) is at base 2436 out of 5536 and is a transition from cytosine to thymine. The mutation is predicted to remove an Arginine and introduce a premature stop codon after residue 738. The missing 342 C‐terminal residues includes the entire SH3 domain of AnHof1. We cloned the wildtype version of AnHof1 into plasmid pRG3 and complemented the phenotype in RCH59, confirming that the mutation occurs in AnHof1. We also deleted AnHof1 to demonstrate that a AnHof1 minus strain has an aseptate phenotype. In the yeasts (S. cerevisiae and S. pombe), Hof1 forms a ring structure that co‐localizes with the CAR and is involved with mediating the cytoskeletal rearrangements necessary for cytokinesis. We GFP tagged AnHof1 to demonstrate that the protein product localizes to sites of septum formation and co‐localizes with actin during at least part of CAR assembly and constriction. In further work, we have generated double‐mutant strains in which a GFP‐tagged septation‐related protein is expressed in the RCH59 strain to demonstrate a network of genetics interactions between AnHof1 and other proteins involved in septation.Support or Funding InformationThis research was supported by NSF grant RUI‐0742907 to TWH and LJH and NSF grant RUI‐1615192 to LJH and TWH.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The inadvertent introduction and rapid spread of chestnut blight (caused by Cryphonectria parasitica (Murr.) Barr) in the early 20th century resulted in the demise of American chestnut (Castanea dentata (Marsh.) Borkh.; Fagaceae) as a major component of forest canopies and had negative impacts on eastern forest communities. Research efforts over the last century have documented the persistence of occasional trees and root crown/stump sprouts throughout much of the historic range of the species providing the basis for ongoing breeding of blight-resistant stock and restoration efforts. Unfortunately, it remains unclear how much of the historic range remains climatically suitable for remnant trees that may harbor unique genetic variation for successful reintroduction efforts. Here we investigate whether the southwestern portion of the historical range remains environmentally suitable for undiscovered remnant populations of C. dentata using environmental niche modeling. We also use stage-structured matrix projection models to investigate the potential demographic future of C. dentata in W Tennessee, N Mississippi, SW Kentucky, and NW Alabama based upon observations of American chestnut in these areas over the last several decades. We found that suitable habitat associated with higher elevations and areas of high forest canopy cover occurs throughout much of southwestern portion of the historical range and that populations of American chestnut in these areas are predicted to drastically decline over the next ~100-200 years without conservation interventions to mitigate the negative consequences of chestnut blight.