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Polarized growth drives the morphogenesis of elongated cellular structures. In plants, polarized growth depends on actin and a tip focused ionic calcium gradient. How the calcium gradient is maintained remains unclear. We discovered that autoinhibitory calcium ATPases (ACAs) redundantly contribute to the steepness of the calcium gradient. ACA1 and ACA2 localize to the subapical plasma membrane and ACA5 to the vacuole membrane, providing spatial regulation of calcium efflux. Tip-growing plant cells also exhibit apical calcium fluctuations. Even though Δaca1/2/5 cells have a diminished calcium gradient, they exhibit normal fluctuations and actin but have significantly reduced apical secretion. Furthermore, cells lacking apical actin retain a strong calcium gradient but have reduced apical secretion. Suppression of both the calcium gradient and apical actin dramatically impairs growth, supporting a model where two independent and parallel processes, the calcium gradient and apical actin, promote rapid polarized growth. 

The NIS synthetase family of enzymes responsible for the biosynthesis of siderophores is increasingly associated with bacterial virulence. Proteins in this class represent outstanding potential drug targets, assuming that basic biochemical and structural characterizations can be completed. Towards this goal, we have mated an improved synthesis of the non-commercial amino acid N-hydroxy-N-succinylcadaverine (HSC, 6) with an isothermal titration calorimetry (ITC) assay that profiles the iterative stages of HSC trimerization and macrocyclization by NIS synthetase DesD from Streptomyces coelicolor. HSC synthesis begins with multigram-scale Gabrielle and tert-butyl N-(benzyloxy)carbamate alkylations of 1-bromo-5-chloropentane following prior literature, but the end-game reported herein has two advantages for greater material throughput: (1) hydrogenolysis of benzyl ether and Cbz blocking groups is best accomplished with Pearlman’s catalyst at 40 psi of H2 and (2) purification of neutral (zwitterionic) HSC is effected by simple flash chromatography over silica gel in MeOH. HSC is subsequently shown to be a substrate for NIS synthetase DesD, which catalyzes three successive amide bond syntheses via adenyl monophosphate ester intermediates. We quantify and present the iterative and overall enzyme kinetic constants associated with formation of the cyclotrimeric siderophore desferrioxamine E (dfoE, 1). 

In an effort to increase community college (CC) biology education research (BER), an NSF-funded network called CC Bio INSITES (Community College Biology Instructor Network to Support Inquiry into Teaching and Education Scholarship; INSITES for short) was developed to provide intellectual, resource, and social support for CC faculty (CCF) to conduct BER. To investigate the efficacy of this network, we asked about the barriers and supports INSITES CCF have experienced when conducting BER and how specific INSITES supports have mitigated barriers and provided support for network members to engage in BER. We conducted interviews and focus groups with 17 network participants, representing 15 different CCs. Qualitative thematic analysis revealed six main barriers that INSITES CCF experience when conducting BER: time constraints, knowledge, incentives or rewards, administrative or peer support, infrastructure, and stigma or misconceptions associated with being CCF. Participants indicated how the supports provided by INSITES helped to mitigate each barrier. Social support was especially critical for CCF to develop a sense of belonging to the CC BER community, though that did not extend to the broader BER community. We describe how these supports function to support BER and recommend four actions for future support of CCF conducting BER.