AUTHOR=Singh Shailendra P. , Montgomery Beronda L. 

TITLE=Regulation of BolA abundance mediates morphogenesis in Fremyella diplosiphon

JOURNAL=Frontiers in Microbiology

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2015.01215

DOI=10.3389/fmicb.2015.01215

ISSN=1664-302X

ABSTRACT=<p>Filamentous cyanobacterium <italic>Fremyella diplosiphon</italic> is known to alter its pigmentation and morphology during complementary chromatic acclimation (CCA) to efficiently harvest available radiant energy for photosynthesis. <italic>F. diplosiphon</italic> cells are rectangular and filaments are longer under green light (GL), whereas smaller, spherical cells and short filaments are prevalent under red light (RL). Light regulation of <italic>bolA</italic> morphogene expression is correlated with photoregulation of cellular morphology in <italic>F. diplosiphon</italic>. Here, we investigate a role for quantitative regulation of cellular BolA protein levels in morphology determination. Overexpression of <italic>bolA</italic> in WT was associated with induction of RL-characteristic spherical morphology even when cultures were grown under GL. Overexpression of <italic>bolA</italic> in a Δ<italic>rcaE</italic> background, which lacks cyanobacteriochrome photosensor RcaE and accumulates lower levels of BolA than WT, partially reverted the cellular morphology of the strain to a WT-like state. Overexpression of BolA in WT and Δ<italic>rcaE</italic> backgrounds was associated with decreased cellular reactive oxygen species (ROS) levels and an increase in filament length under both GL and RL. Morphological defects and high ROS levels commonly observed in Δ<italic>rcaE</italic> could, thus, be in part due to low accumulation of BolA. Together, these findings support an emerging model for RcaE-dependent photoregulation of BolA in controlling the cellular morphology of <italic>F. diplosiphon</italic> during CCA.</p>