Early candidacy for differentiation into heterocysts in the filamentous cyanobacterium Anabaena sp. PCC 7120
- 256 Downloads
The filamentous cyanobacterium Anabaena sp. PCC 7120 fixes dinitrogen facultatively. Upon depletion of combined nitrogen, about 10% of vegetative cells within the filaments differentiate terminally into nitrogen-fixing cells. The heterocyst has been studied as a model system of prokaryotic cell differentiation, with major focus on signal transduction and pattern formation. The fate of heterocyst differentiation is determined at about the eighth hour of induction (point of no return), well before conspicuous morphological or metabolic changes occur. However, little is known about how the initial heterocysts are selected after the induction by nitrogen deprivation. To address this question, we followed the fate of every cells on agar plates after nitrogen deprivation with an interval of 4 h. About 10% of heterocysts were formed without prior division after the start of nitrogen deprivation. The intensity of fluorescence of GFP in the transformants of hetR-gfp increased markedly in the future heterocysts at the fourth hour with respect to other cells. We also noted that the growing filaments consisted of clusters of four consecutive cells that we call quartets. About 75% of initial heterocysts originated from either of the two outer cells of quartets at the start of nitrogen deprivation. These results suggest that the future heterocysts are loosely selected at early times after the start of nitrogen deprivation, before the commitment. Such early candidacy could be explained by different properties of the outer and inner cells of a quartet, but the molecular nature of candidacy remains to be uncovered.
KeywordsFilamentous cyanobacteria Anabaena sp. PCC 7120 Heterocyst candidacy Differentiation Cell lineage Cell division Pattern formation Frequently iterated observation Spatial periodicity Quartet
Green fluorescent protein
Heterocyst lineage description system
Maximum entropy method
This work was supported in part by Grants-in-Aid from MEXT (17018010, 18017005, 20017006) and JSPS (16GS00304), Japan, to N. S, a Grant-in-Aid from JSPS (2011425) to N. V. S, and Global COE Program (Integrative Life Science Based on the Study of Biosignaling Mechanisms), MEXT, Japan to M. T.
- Burg JP (1967) Maximum entropy spectral analysis in Proc. 37th Meet. Soc. Exploration Geophysicists. In: Childers DG (ed) Modern spectrum analysis. IEEE Press, New York, pp 34–41Google Scholar
- Peterson RB, Shaw ER, Dolan E, Ke B (1981) A photochemically active heterocyst preparation from Anabaena variabilis. Photobiochem Photobiophys 2:79–84Google Scholar
- Rippka R, Deruelles J, Waterbury JB, Herdman M, Stanier RY (1979) Genetic assignments, strain histories and properties of pure cultures of cyanobacteria. J Gen Microbiol 111:1–61Google Scholar
- Wolk CP (2000) Heterocyst formation in Anabaena. In: Brun YV, Shimkets LJ (eds) Prokaryotic development. American Society for Microbiology, Washington, DC, pp 83–104Google Scholar