Genome-wide survey of heat shock proteins (HSP) and expression analysis of HSP genes under abiotic stress conditions in some populus taxons

Heat shock proteins (Hsps) are a group of proteins found in living organisms and also called stress proteins. Heat-shock protein genes play a key role in the regulation of the changes at the moment of stress (salinity, drought, heavy metal and extreme temperature etc.). Molecular-based studies on the response mechanisms of forest trees to abiotic stresses In 2006, it was started on "Populus trichocarpa" type, whose genome sequence was completed as a model tree species. In recent years bioinformatic analyzes have been carried out to determine functional gene regions of the species. In this thesis work consists of two parts. In the first chapter; identification of all Hsps (sHsp, Hsp40, Hsp60, Hsp70, Hsp90 and Hsp100) gene family members by using bioinformatic methods, distribution on chromosomes, calculation of tandem and segmental duplications, phylogenetic analysis, prediction of gene structure, extraction of conserved motif regions, gene ontology categories, three-dimensional modeling of proteins, detection of miRNA target genes and comparison with Hsps proteins found in other plant species. As a result of bioinformatic analyzes made on P. trichocarpa genome; 60, 145, 49, 34, 12 and 90 genes belonging to members of sHsp, Hsp40, Hsp60, Hsp70, Hsp90 and Hsp100 genes families were firstly defined within the scope of this thesis. In this study, a total of 390 genes belonging to all Hsps gene families were identified. Bioinformatic approaches can also determine the genetic pathways of the resistance mechanism to abiotic stresses. In the second part of the thesis study, expression levels of genes encoding Hsps proteins were investigated using transcriptomic data (RNASeq and Microarray) found in the databases. Increased gene expression levels; it can be thought that the detected gene (the expression of the growing gene) acts as a protective molecule against the stresses. In addition, the expression levels of the Hsps genes identified in the poplar clones under drought, salinity and cadmium stress were examined using qRT-PCR (real-time PCR) method using leaf tissues of poplar clones. Thus, it is aimed that to analyze the functions of this important gene family and to determine the poplar taxons which are resistant to the determined stresses. As a result; For drought stress; The PtHsp70-25 and PtHsp70-33 genes are high expression only for the resistant clone under stress conditions and can be said to have a protective role against the plant. The gene expression levels of PtHsp70-16 and PtHsp70- 26 genes were high in both sensitive (Clone A: N03.368A) and resistant (Clone B: N.62.191) clones. For this reason, it can be speculated that these genes play a key role in responding to drought stress. For salinity stress; PtsHsp-11, PtsHsp-21, PtsHsp-36, PtHsp40-113, PtHsp40-117, PtHsp60-31, PtHsp60-33, PtHsp60-38, PtHsp60-49, PtHsp70-09, PtHsp70-12, 33, PtHsp90-09, PtHsp90-12, PtHsp100-21, and PtHsp100-75 expression levels of genes were increased. In the cadmium stress conditions; PtsHsp-44, PtsHsp-54, PtHsp40-117, PtHsp60-06, PtHsp60-12, PtHsp70-21, PtHsp70-28, PtHsp90-02, PtHsp90-10, PtHsp90-12, PtHsp100-22, and PtHsp100-71 the expression levels of the genes were high. In addition, it was determined that the highest level of cadmium accumulation of the root in poplar taxa. With this thesis study, it is anticipated that new possibilities will be provided for gene cloning and functional analyzes that can be used in subsequent studies to improve stress tolerance in plants. In this regard, plants have obtained preliminary information on molecular mechanisms related to stress, which will enable the production of new projects. As a result, defining this genomic analysis will provide a new perspective for future work on other forest trees in terms of developing tolerance against poplar, which is an important species for rapidly developing and deficit in Turkish wood raw materials.