Mitochondrial Stress-Responsive Nuclear Encoded

Question: Describe about the Mitochondrial Stress-Responsive for Nuclear Encoded. Answer: 1. To identify the mutations in the mitochondrial retrograde signalling pathway under stress in plants the researcher conducted a genetic screen where AOX1a is used as model. This AOX1a is a mitochondrial stress-responsive and nuclear-encoded component. Along with AOX1a a construct was added in the position of 2kb upstream region of promoter which drives a luciferase gene of firefly AOX1a-LUC and is utilized as a reporter gene and enduringly gets changed into Arabidopsis thaliana Columbia-0 which generates Col: LUC germ lines. After two weeks this Col:LUC seedlings shows a high expression of LUC gene driven by the promoter AOX1a when they are treated with 50 M of antimycin A (Ivanova et al. 2014 pp.1233-1254). The mutation in ANAC017 encoding gene inhibits the transcription as it ANAC017 is the transcription factor and the protein is encoded by only one gene. The gene lines rao2-2 and rao2-1 both are the recessive type of mutations and that are mapped on the 2.47-Mb region on chromos ome 1 between the In/Del CEREON Genomics markers CER450671 and CER449719. However the ANAC017-2 mutation is a dominant mutation (Ng et al. 2013 pp.3449-3459). 2. The evidence from the recent studies shows that ANAC017 is a transcription factor is a particular gene present at the locus At1g34190 which encodes for a NAC domain transcription factor ANAC017 that was identified with a mutation in each of the alleles of mutant and as a result of this the transgenic plant loses its ability to induce AOX1a-LUC. On the other hand when the coding sequence of the wild type of At1g34190 was expressed underneath the control of 35s promoter of the cauliflower mosaic virus and transmuted into rao2-1 mutants and restores the capability of the transgenic plant to stimulate AOX1a-LUC under AA treatment. Hence it is confirmed that rao2 phenotype was the result of a particular mutation that occurred in ANAC017 (Van Aken et al. 2016). It is quite evident from this that ANAC017 is the transcription factor and any type of mutation in ANAC017 will affect the transcription. The promoter to which ANAC017 bounded is AOX1a (Hofmann, 2013 pp.3151-3151). 3. To obtain the evidence about ANAC017 a design of a particular construct was made which was tagged with red fluorescent protein (RFP) at the N terminus and a green fluorescent protein (GFP) at the C terminus. The test results with this construct shows that as the GFP is at C terminus therefore green fluorescence will be visible or observed in the Endoplasmic Reticulum (ER) and this green fluorescence will remain inside the ER even when the N terminal portion of the ANAC017 have been released by proteolysis. Now as the RFP is at the N terminus, it has been proposed that along with being located in the ER, this portion or fragment will also be located to the nucleus and finally when treated with antimycin A (AA) the amount of RFP in the nucleus is found to increase in comparison to the RPF in the ER. Nevertheless, the green fluorescence was restricted to the ER and the red fluorescence distinctly detected both in nucleus and in ER. Along with this when a construct that is dual-tagged with fluorescent protein labelling at ER and actin established that GFP coincides with ER and actin and the RFP is detected both in the nucleus and in the ER present at the outside of the nucleus. Hence, these evidences show that ANAC017 is cleaved from ER and moved to Nucleus. The physiological sensitivity in according to environmental stress and H2O2 in all the transgenic plants can be summarised in the way that changes that happened were examined by the use of microarray examination. The AA acts as an inhibitor for the electron transport of mitochondria and in addition with this it is the H2O2 which is actuality produced in the mitochondria by means of the manganese superoxide dismutase forms superoxide radical (O-2) which is highly reactive. This superoxide radical are produced by different cellular sources. Both the H2O2 and AA stress treatments, transcripts were catalogued into any one of the five genes sets based on the changes in the transcript profusion in the response to the stress in the wild types against the mutant lines. The total proportion of stress reactive transcriptomic changes which are facilitated through ANAC017 function were scrutinised for two stress treatments and linked with the percentages of stress responsive changes which mediat es independently of ANAC017 function (Pongprayoon et al. 2013 pp.159-173). Reference Hofmann, N.R., 2013. Endoplasmic ReticulumLocalized Transcription Factors and Mitochondrial Retrograde Regulation. The Plant Cell, 25(9), pp.3151-3151. Ivanova, A., Law, S.R., Narsai, R., Duncan, O., Lee, J.H., Zhang, B., Van Aken, O., Radomiljac, J.D., van der Merwe, M., Yi, K. and Whelan, J., 2014. A functional antagonistic relationship between auxin and mitochondrial retrograde signaling regulates alternative oxidase1a expression in Arabidopsis. Plant physiology, 165(3), pp.1233-1254. Ng, S., Giraud, E., Duncan, O., Law, S.R., Wang, Y., Xu, L., Narsai, R., Carrie, C., Walker, H., Day, D.A. and Blanco, N.E., 2013. Cyclin-dependent kinase E1 (CDKE1) provides a cellular switch in plants between growth and stress responses. Journal of Biological Chemistry, 288(5), pp.3449-3459. Pongprayoon, W., Roytrakul, S., Pichayangkura, R. and Chadchawan, S., 2013. The role of hydrogen peroxide in chitosan-induced resistance to osmotic stress in rice (Oryza sativa L.). Plant Growth Regulation, 70(2), pp.159-173. Van Aken, O., Ford, E., Lister, R., Huang, S. and Millar, A.H., 2016. Retrograde signalling caused by heritable mitochondrial dysfunction is partially mediated by ANAC017 and improves plant performance. The Plant Journal.