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Nuclear activity and star-formation activity are two important processes that can shape galaxies. This thesis is dedicated to studying the most extreme nuclear activity and star-formation activity in our Universe. First I study the widely-debated topic about whether galaxy mergers can trigger active galactic nuclei (AGNs) and whether there exists difference of impact in triggering different types of AGNs. Then I study extreme dusty star-forming galaxies by selecting a parent sample of infrared (IR) luminous galaxies based on Herschel space telescope object catalogs. I propose a novel method to deblend Herschel imaging based on the tight correlation between radio and far-IR. Furthermore, I investigate the physical properties of the most extreme hyperluminous infrared galaxies in detail and their relation across cosmic time. Finally, I study the small-scale environment of these HLIRGs by searching for their neighbours and comparing with random positions.

Feedback from low-excitation radio galaxies (LERGs) plays a key role in the lifecycle of massive galaxies in the local Universe; their evolution, and the impact of these active galactic nuclei on early galaxy evolution, however, remain poorly understood. We use a sample of 10481 LERGs from the first data release of the LOFAR Two-meter Sky Survey Deep Fields, covering $\sim$ 25 deg$^2$, to present the first measurement of the evolution of the radio luminosity function (LF) of LERGs out to $z\sim2.5$; this shows relatively mild evolution. We split the LERGs into those hosted by quiescent and star-forming galaxies, finding a new dominant population of LERGs hosted by star-forming galaxies at high redshifts. The incidence of LERGs in quiescent galaxies shows a steep dependence on stellar-mass out to $z \sim1.5$, consistent with local Universe measurements of accretion occurring from cooling of hot gas haloes. The quiescent-LERGs dominate the LFs at $z, 26 pages, 16 figures, accepted for publication in MNRAS. LF data available at: https://github.com/rohitk-10/AGN_LF_Kondapally22 . Author list error corrected in updated version

The eastern Asian and eastern North American disjunction in Juglans offers an opportunity to estimate the time since divergence of the Eurasian and American lineages and to compare it with paleobotanical evidence. Five chloroplast DNA noncoding spacer (NCS) sequences: trnT−trnF, psbA−trnH, atpB−rbcL, trnV-16S rRNA, and trnS-trnfM and data from earlier studies (matK, ITS, and nuclear RFLP) were used to reconstruct phylogeny and to estimate the divergence time of major lineages. Seventeen taxa from four sections of Juglans and two outgroup taxa, Pterocarya stenoptera and Carya illinoiensis were included. NCS data was congruent only with matK data. Both maximum parsimony (MP) and maximum likelihood (ML) cladograms were concordant at the sectional level and revealed three well-supported monophyletic clades corresponding to sections Juglans, Cardiocaryon, and Rhysocaryon in both NCS and combined analyses. The single extant American butternut, Juglans cinerea was placed within the poorly resolved, but well-supported Rhysocaryon. Placement of taxa within Rhysocaryon and Cardiocaryon were inconsistent between NCS and combined analyses. Overall, the results suggest that: (1) the NCS sequence divergence observed within and between sections of Juglans is low and the addition of matK data only marginally improved resolution within Rhysocaryon; (2) the early divergence of section Juglans in both MP and ML analyses of NCS and combined data implies its ancient origin in contrast to fossil evidence, which suggests the earliest divergence of sections Rhysocaryon and Cardiocaryon; and (3) the extant taxa may not hold the footprints to unravel the evolutionary history of the genus.

One of the most important rootstocks in the California walnut industry is Paradox, which refers to the offspring of a California black walnut pollinized by a Persian walnut ( Juglans regia ). Paradox was developed by Luther Burbank, who did not distinguish between northern ( J. hindsii ) and southern ( J. californica ) California black walnut. Although it is generally accepted that Paradox designates hybrids between J. hindsii and J. regia , the name is commonly applied to any black walnut–Persian walnut hybrid. Moreover, due to gene flow among black walnut species, the genealogy of Paradox hybrids may also include species such as Arizona ( J. major ) and Eastern black ( J. nigra ) walnut. Since the nuts from which Paradox seedlings are grown are collected from wild trees, their genetic backgrounds are not generally known. In conjunction with a large study aimed at evaluating Paradox hybrids from different industry sources, we have been working to develop molecular markers that can be used to infer the parentage of individual Paradox seedlings. Representatives of the five black walnut species from North America were screened for variability in the internal transcribed spacer (ITS) regions of the nuclear ribosomal DNA and in three noncoding regions from the chloroplast genome, the trn T– trn L, trn L– trn F, and trn D– trn T spacers. Unique sequence markers were identified for each species, and total DNA extracts from 27 Paradox source trees were tested for those markers. Chloroplast DNA profiles were used to trace the maternal lineages of the Paradox source trees, while the ITS data provided evidence as to whether or not the source trees were themselves hybrids. Our results indicate that, among industry Paradox sources, there is considerable genetic contribution from species other than J. hindsii .

Phylogenetic relationships in Rosaceae were studied using parsimony analysis of nucleotide sequence data from two regions of the chloroplast genome, the matK gene and the trnL-trnF region. As in a previously published phylogeny of Rosaceae based upon rbcL sequences, monophyletic groups were resolved that correspond, with some modifications, to subfamilies Maloideae and Rosoideae, but Spiraeoideae were polyphyletic. Three main lineages appear to have diverged early in the evolution of the family: 1) Rosoideae sensu stricto, including taxa with a base chromosome number of 7 (occasionally 8); 2) actinorhizal Rosaceae, a group of taxa that engage in symbiotic nitrogen fixation; and 3) the rest of the family. The spiraeoid genus Gillenia, not included in the rbcL study, was strongly supported as the sister taxon to Maloideae sensu lato. A New World origin of Maloideae is suggested. The position of the economically important genus Prunus and the status of subfamily Amygdaloideae remain unresolved.

The utility of intersimple sequence repeat (ISSR) markers for identification of English or Persian walnut (Juglans regia L.) cultivars was explored. Four cultivars were screened with 47 ISSR primers; eight of these primers, which generated reproducible and informative data, were selected for further study. Two individuals from each of 48 cultivars, including many currently important in the California walnut industry as well as accessions from Europe and Asia, were then examined with the eight ISSR primers. Polymerase chain reaction (PCR) products were separated on agarose gels and stained with ethidium bromide. Fifty-four bands were scored as present or absent in each cultivar; of these, 31 (57%) were polymorphic among the 48 cultivars. Combined data from the eight ISSR primers provided a unique fingerprint for each of the cultivars tested. Fifteen of the cultivars could be distinguished from all others with just one primer, 31 with a minimum of two primers, and two required three primers. Pairwise genetic distances between the cultivars were calculated and a dendrogram was generated using the neighbor-joining algorithm. Some of the groupings in the dendrogram corresponded to groups which, based on known pedigrees, are genealogically closely related. Others included accessions from diverse genetic and/or geographic origins. These results can be attributed to a combination of the limitations of the ISSR method for inferring genetic relationships, on the one hand, and the complex history of walnut cultivar development involving extensive exchange and breeding of germplasm from different geographic regions, on the other.

Nogo receptor 1 (NgR1) mediates the inhibitory effects of several myelin-associated inhibitors (MAIs) on axonal regeneration in the central nervous system. A truncated soluble NgR1 (sNgR) has been reported to act as a decoy receptor to block the actions of MAIs. In this study, we fused the sNgR to nerve growth factor (NGF) and used NGF as a carrier to deliver sNgR to the intercellular space to neutralize MAIs. NGF in NGF–sNgR remained biologically active and induced sprouting of calcitonin gene related peptide containing axons when expressed in the spinal cord using a lentiviral vector (LV). Secreted NGF–sNgR promoted neurite outgrowth of dissociated dorsal root ganglion neurons on myelin protein substrate. In a rat dorsal column transection model, regenerating sensory axons were found to grow into the lesion cavity in animals injected with LV/NGF–sNgR, while in animals injected with LV/GFP or LV/NGF–GFP few sensory axons entered the lesion cavity. The results indicate that NGF–sNgR fusion protein can reduce the inhibition of MAIs and facilitate sensory axon regeneration. The fusion constructs may be modified to target other molecules to promote axonal regeneration and the concept may also be adapted to develop gene therapy strategies to treat other disorders.

To evaluate the value of three-dimensional (3D) digital subtraction angiography (DSA) in diagnosis and planning endovascular treatment of cerebrovascular diseases.Standard DSA and 3D-DSA were performed in 40 adult patients (aged 21 approximately 74 years) suspected to be with cerebrovascular diseases. The schemes of endovascular treatment were worked out according to the results of 3D-DSA.Positive rate of standard DSA and 3D-DSA were 85.0% and 95.0% respectively in diagnosis of cerebrovascular diseases. 100% occlusion was achieved in 11 patients with intracranial aneurysms and in 7 patients with arteriovenous malformations, and 100% recanalization was achieved in 9 patients with ischemic stroke. Temporary complications were found in 3 of all patients (7.9%).3D-DSA is an ideal tool superior to standard DSA in diagnosis of cerebrovascular diseases and has potential value for evaluating endovascular treatment of cerebrovascular diseases.