Joined in 2023 
82 
63 About this deal
Zhang JY, Chen WL, Zhang CC: hetR and patS, two genes necessary for heterocyst pattern formation, are widespread in filamentous nonheterocyst-forming cyanobacteria. Microbiology. 2009, 155 (Pt 5): 1418-1426. 10.1099/mic.0.027540-0. Feldmann, E. A. et al. Differential binding between PatS C-terminal peptide fragments and HetR from Anabaena sp. PCC 7120. Biochemistry 51, 2436–42 (2012). In this section we translate the genetic circuit previously described into a set of differential equations, for which we follow the derivation in [ 46– 48]. Details are left to supplementary information ( S1 text). To simplify notation, constants related to NtcA, HetR, PatS and cN are denoted with the letters a, r, s, and n respectively.
Purified HetR and mutants were dialyzed against a buffer containing 1 M NaCl, 5% (v/v) glycerol and 10 mM Tris-Cl, pH 7.8 for 12 hr. The data were collected on an iTC200 (MicroCal) at 25 °C by injecting an initial 0.4 μl aliquot and the following 19 consecutive 2 μl aliquots. The sample cell was loaded with 200 μl protein while the injection syringe was loaded with 40 μl PatS6. The wild-type HetR, mutants E254A and D256A were diluted to a final concentration of 10 μM, whereas the concentration of mutants R223W, E253A, D270A, D278A, D270A/D278A and HetR Hood was 50 μM. The concentration of PatS6 was 15 times (150 or 750 μM) to that of the full-length protein or 40 times (2 mM) to that of HetR Hood. EMSA assays However, it remained unclear how the nitrogen-fixing cell could ignore its own PatS signal and keep its HetR signal active. HetL – another protein produced by the future nitrogen-fixing cell – could potentially play this role, but how it acts was unknown. Schneider CA, Rasband WS, Eliceiri KW: NIH Image to ImageJ: 25 years of image analysis. Nat Methods. 2012, 9 (7): 671-675. 10.1038/nmeth.2089.
Laurent S, Chen H, Bédu S, Ziarelli F, Peng L, Zhang CC (2005) Nonmetabolizable analogue of 2-oxoglutarate elicits heterocyst differentiation under repressive conditions in Anabaena sp. PCC 7120. P Natl Acad Sci USA 102: 9907–9912. Murray JD (2003) Mathematical Biology II: Spatial Models and Biomedical Applications computational model predicts phenotype from genotype. New York: Springer-Verlag, third edition. It would be good to have a title that captures the broader significance of the work. Maybe something like: "HetL, HetR and PatS form a reaction-diffusion system for pattern formation in the filamentous cyanobacterium Nostoc" Koch A, Meinhardt H (1994) Biological pattern formation: from basic mechanisms to complex structures. Rev Mod Phys 66: 1481–1511.
The model is rounded off by coupling a number of cells in a one-dimensional array so that combined nitrogen and PatS can diffuse along the cellular chain. We have shown that one important ingredient affecting the dynamical behavior of the chain is noise, which plays a key role in onset of the pattern formation, i.e., the transition from the initial chain of vegetative cells to the steady state in which heterocysts coexist with vegetative cyanobacteria. Thus, the appearance of differentiation is, in our model, a pure stochastic event. The cooperative character of the filament is clear from the amount of noise needed to start the differentiation process which appears significantly smaller than that needed in isolated cells. The source of noise as well as its biological consequences is, nowadays a current topic of research [ 58]. In fact, at its initial state, differentiation of cells appears randomly along the filament, but shortly after its onset a characteristic distribution of heterocyst emerges. This distribution can be compared with the experimental one with a fairly good agreement [ 41].Mitchison GJ, Wilcox M, Smith RJ (1976) Measurement of an inhibitory zone. Science 191: 866–868. pmid:814620 With the implementation of initiatives under the recently unveiled National Energy Transition Roadmap (NETR) and (now) the HETR, Malaysia is set to be at the forefront of becoming a regional leader in the energy transition and renewable energy industry,” he said at the launch of IGEM 2023. Fig 1. Main components and interactions involved in the reaction to combined nitrogen deprivation in cyanobacteria. Flaherty BL, Van Nieuwerburgh F, Head SR, Golden JW: Directional RNA deep sequencing sheds new light on the transcriptional response of Anabaena sp. strain PCC 7120 to combined-nitrogen deprivation. BMC Genomics. 2011, 12 (1): 332-10.1186/1471-2164-12-332.
Corral Borthakur PB, Orozco CC, Young-Robbins SS, Haselkorn R, Callahan SM (2005) Inactivation of patS and hetN causes lethal levels of heterocyst differentiation in the filamentous cyanobacterium Anabaena sp. PCC 7120. Mol microbiol 57: 111–123. pmid:15948953 Higa, K. C. et al. The RGSGR amino acid motif of the intercellular signalling protein, HetN, is required for patterning of heterocysts in Anabaena sp. strain PCC 7120. Mol. Microbiol. 83, 682–93 (2012). The HETR implementation alone is anticipated to have prospects of generating up to RM12.1 billion in revenue with an estimated contribution of between RM49 billion and RM61 billion to gross domestic product by 2030, generating over 45,000 job opportunities over the same period.
Cells can communicate and establish patterns by exchanging molecular signals that switch on and off certain cell programs. For instance, a protein called HetR turns on the genetic program that allows cyanobacteria to fix nitrogen; on the other hand, a signal known as PatS binds to HetR and turns it off. Cells starting to specialise in fixing nitrogen produce both HetR and PatS, with the latter diffusing in surrounding cells and preventing them from extracting nitrogen.
Great Deal 
New Comment