An amidase is required for proper intercellular communication in the filamentous cyanobacteriumAnabaenasp. PCC 7120.
Channels that cross cell walls and connect the cytoplasm of neighboring cells in multicellular cyanobacteria are pivotal for intercellular communication. We find that the product of the geneall1140of the filamentous cyanobacteriumAnabaenasp. PCC 7120 is required for proper channel formation.All1140encodes an amidase that hydrolyses purified peptidoglycans. An All1140-GFP fusion protein is located at the Z-ring in the periplasmic space during most of the cell cycle. Anall1140-null mutant (M40) was unable to grow diazotrophically, and no mature heterocysts were observed in the absence of combined nitrogen. Expression of two key genes,hetRandpatS, was studied in M40 using GFP as a reporter. Upon nitrogen step-down, the patterned distribution of green fluorescent cells in filaments seen in the wild type were not observed in mutant M40. Intercellular communication in M40 was studied by measuring fluorescence recovery after photobleaching (FRAP). Movement of calcein (622 Da) was aborted in M40, suggesting that the channels connecting the cytoplasm of neighboring cells are impaired in the mutant. The channels were examined with electron tomography; their diameters were nearly identical, 12.7 nm for the wild type and 12.4 nm for M40, suggesting that AmiC3 is not required for channel formation. However, when the cell wall sacculi isolated by boiling were examined by EM, the average sizes of the channels of the wild type and M40 were 20 nm and 12 nm, respectively, suggesting that the channel walls of the wild type are expandable and that this expandability requires AmiC3.
State Key Laboratory of Protein and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing 100871, People's Republic of China.
Zhenggao
Z
Zheng
Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637.
Amin
A
Omairi-Nasser
State Key Laboratory of Protein and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing 100871, People's Republic of China.
Xiying
X
Li
State Key Laboratory of Protein and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing 100871, People's Republic of China.
Chunxia
C
Dong
Chinese Academy of Sciences Key Laboratory of Phycological Research, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, People's Republic of China.
Yan
Y
Lin
Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637; jzhao@pku.edu.cn rh01@uchicago.edu.
Robert
0000-0003-4094-3524
R
Haselkorn
State Key Laboratory of Protein and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing 100871, People's Republic of China; jzhao@pku.edu.cn rh01@uchicago.edu.|Chinese Academy of Sciences Key Laboratory of Phycological Research, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, People's Republic of China.
Jindong
J
Zhao
D000581:Amidohydrolases / Q000378:metabolism*; D017033:Anabaena / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D002450:Cell Communication / Q000502:physiology*; D002473:Cell Wall / Q000378:metabolism; D000458:Cyanobacteria / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D036681:Fluorescence Recovery After Photobleaching / Q000379:methods; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D010457:Peptidoglycan / Q000378:metabolism; D019897:Periplasm / Q000378:metabolism
D001426:Bacterial Proteins; D010457:Peptidoglycan; D049452:Green Fluorescent Proteins; D000581:Amidohydrolases; C019665:amidase; D009584:Nitrogen
channels; cyanobacteria; intercellular communication; peptidoglycan