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Fremyella diplosiphon is a well-studied a model cyanobacterium for photosynthesis due to its efficient light absorption potential and pigment accumulation. In the present study, the impact of ampicillin, tetracycline, kanamycin, and cefotaxime on pigment fluorescence and photosynthetic capacity in Fremyella diplosiphon strains B481-WT and B481-SD was investigated. Our results indicated that both strains exposed to kanamycin from 0.2 to 3.2 mg/L and tetracycline from 0.8 to 12.8 mg/L enhanced growth and pigment accumulation. Additionally, B481-SD treated with 0.2–51.2 mg/L ampicillin resulted in a significant enhancement of pigment fluorescence. A detrimental effect on growth and pigmentation in both the strains exposed to 6.4–102.5 mg/L kanamycin and 0.8–102.5 mg/L cefotaxime was observed. Detection of reactive oxygen species revealed highest levels of oxidative stress at 51.2 and 102.5 mg/L kanamycin for B481- SD and 102.5 mg/L for B481-WT. Membrane permeability detected by lactate dehydrogenase assay indicated maximal activity at 0.8 mg/L ampicillin, kanamycin, and tetracycline treatments on day 6. Abundant vacuolation, pyrophosphate, and cyanophycin granule formation were observed in treated cells as a response to antibiotic stress. These findings on the hormetic effect of antibiotics on F. diplosiphon indicate that optimal antibiotic concentrations induce cellular growth while high concentrations severely impact cellular functionality. Future studies will be aimed to enhance cellular lipid productivity at optimal antibiotic concentrations to disintegrate the cell wall, thus paving the way for clean bioenergy applications.
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CYTOKININ RESPONSE FACTOR 2 is involved in modulating the salt stress response
SUMMARY Cytokinin has strong connections to development and a growing role in the abiotic stress response. Here we show that CYTOKININ RESPONSE FACTOR 2 (CRF2) is additionally involved in the salt (NaCl) stress response. CRF2 promoter‐GUS expression indicates CRF2 involvement in the response to salt stress as well as the previously known cytokinin response. Interestingly, CRF2 mutant seedlings are quite similar to the wild type (WT) under non‐stressed conditions yet have many distinct changes in response to salt stress. Cytokinin levels measured by liquid chromatography–tandem mass spectrometry (LC‐MS/MS) that increased in the WT after salt stress are decreased incrf2, potentially from CRF2 regulation of cytokinin biosynthesis genes. Ion content measured by inductively coupled plasma optical emission spectrometry (ICP‐OES) was increased in the WT for Na, K, Mn, Ca and Mg after salt stress, whereas the corresponding Ca and Mg increases are lacking incrf2. Many genes examined by RNA‐seq analysis were altered transcriptionally by salt stress in both the WT andcrf2, yet interestingly approximately one‐third of salt‐modifiedcrf2transcripts (2655) showed unique regulation. Different transcript profiles for salt stress incrf2compared with the WT background was further supported through an examination of co‐expressed genes by weighted gene correlation network analysis (WGCMA) and principal component analysis (PCA). Additionally, Gene Ontology (GO) enrichment terms found from salt‐treated transcripts revealed most photosynthesis‐related terms as only being affected incrf2, leading to an examination of chlorophyll levels and the efficiency of photosystem II (via the ratio of variable fluorescence to maximum fluorescence,Fv/Fm) as well as physiology after salt treatment. Salt stress‐treatedcrf2plants had both reduced chlorophyll levels and lowerFv/Fmvalues compared with the WT, suggesting that CRF2 plays a role in the modulation of salt stress responses linked to photosynthesis.
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- Award ID(s):
- 2033337
- PAR ID:
- 10445783
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- The Plant Journal
- Volume:
- 110
- Issue:
- 4
- ISSN:
- 0960-7412
- Page Range / eLocation ID:
- p. 1097-1110
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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