A Ubiquitously Conserved Cyanobacterial Protein Phosphatase Essential for High Light Tolerance in a Fast-Growing Cyanobacterium

Journal Article · Wed Aug 31 00:00:00 EDT 2022 · Microbiology Spectrum

DOI:https://doi.org/10.1128/spectrum.01008-22· OSTI ID:1873197

Walker, Patricia L.  ^[1]; Pakrasi, Himadri B.  ^[1]; Youssef, ed., Noha H.

---

1. Department of Biology, Washington University, St. Louis, Missouri, USA

Synechococcus elongatus UTEX 2973, the fastest-growing cyanobacterial strain known, optimally grows under extreme high light (HL) intensities of 1,500–2,500 μmol photons m^-2 s^-1, which is lethal to most other photosynthetic microbes. We leveraged the few genetic differences between Synechococcus 2973 and the HL sensitive strain Synechococcus elongatus PCC 7942 to unravel factors essential for the high light tolerance. We identified a novel protein in Synechococcus 2973 that we have termed HltA for $$\underline{H}$$igh light tolerance protein $$\underline{A}$$. Using bioinformatic tools, we determined that HltA contains a functional PP2C-type protein phosphatase domain. Phylogenetic analysis showed that the PP2C domain belongs to the bacterial-specific Group II family and is closely related to the environmental stress response phosphatase RsbU. Additionally, we showed that unlike any previously described phosphatases, HltA contains a single N-terminal regulatory GAF domain. We found hltA to be ubiquitous throughout cyanobacteria, indicative of its potentially important role in the photosynthetic lifestyle of these oxygenic phototrophs. Mutations in the hltA gene resulted in severe defects specific to high light growth. These results provide evidence that hltA is a key factor in the tolerance of Synechococcus 2973 to high light and will open new insights into the mechanisms of cyanobacterial light stress response.

• Research Organization: Washington Univ., St. Louis, MO (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF); Washington University in St. Louis
• Grant/Contract Number: FG02-99ER20350; MCB 2037887
• OSTI ID: 1873197
• Alternate ID(s): OSTI ID: 1904569
• Journal Information: Microbiology Spectrum, Journal Name: Microbiology Spectrum Vol. 10 Journal Issue: 4; ISSN 2165-0497
• Publisher: American Society for Microbiology
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
cyanobacteria
high light
stress tolerance
serine/threonine phosphatases