Cloud-Based User Behavior Emulation Approach for Space-Ground Integrated Networks

Cyber-physical systems (CPSs) based on space-ground integrated networks (SGINs) enable CPSs to break through geographical restrictions in space. Therefore, providing a test platform is necessary for new technical verification and network security strategy evaluations of SGINs. User behavior emulation technology can effectively support the construction of a test platform. Given the inherent dynamic changes, diverse behaviors, and large-scale characteristics of SGIN users, we propose user behavior emulation technology based on a cloud platform. First, the dynamic emulation architecture for user behavior for SGINs is designed. Then, normal user behavior emulation strategy driven by the group user behavior model in real time is proposed, which can improve the fidelity of emulation. Moreover, rogue user behavior emulation technology is adopted, based on traffic replay, to perform the security evaluation. Specifically, virtual Internet Protocol (IP) technology and the epoll model are effectively integrated in this investigation to resolve the contradiction between large-scale emulation and computational overhead. The experimental results demonstrate that the strategy meets the requirement of a diverse and high-fidelity dynamic user behavior emulation and reaches the emulation scale of 100,000-level concurrent communication for normal users and 100,000-level concurrent attacks for rogue users

Different Modes of Gene Duplication Show Divergent Evolutionary Patterns and Contribute Differently to the Expansion of Gene Families Involved in Important Fruit Traits in Pear (Pyrus bretschneideri)

Pear is an important fruit crop of the Rosaceae family and has experienced two rounds of ancient whole-genome duplications (WGDs). However, whether different types of gene duplications evolved differently after duplication remains unclear in the pear genome. In this study, we identified the different modes of gene duplication in pear. Duplicate genes derived from WGD, tandem, proximal, retrotransposed, DNA-based transposed or dispersed duplications differ in genomic distribution, gene features, selection pressure, expression divergence, regulatory divergence and biological roles. Widespread sequence, expression and regulatory divergence have occurred between duplicate genes over the 30–45 million years of evolution after the recent genome duplication in pear. The retrotransposed genes show relatively higher expression and regulatory divergence than other gene duplication modes. In contrast, WGD genes underwent a slower sequence divergence and may be influenced by abundant gene conversion events. Moreover, the different classes of duplicate genes exhibited biased functional roles. We also investigated the evolution and expansion patterns of the gene families involved in sugar and organic acid metabolism pathways, which are closely related to the fruit quality and taste in pear. Single-gene duplications largely account for the extensive expansion of gene families involved in the sorbitol metabolism pathway in pear. Gene family expansion was also detected in the sucrose metabolism pathway and tricarboxylic acid cycle pathways. Thus, this study provides insights into the evolutionary fates of duplicated genes

Genome-wide identification and comparative evolutionary analysis of sorbitol metabolism pathway genes in four Rosaceae species and three model plants

In contrast to most land plant species, sorbitol, instead of sucrose, is the major photosynthetic product in many Rosaceae species. It has been well illustrated that three key functional genes encoding sorbitol-6-phosphate dehydro- genase (S6PDH), sorbitol dehydrogenase (SDH), and sorbitol transporter (SOT), are mainly responsible for the synthesis, degradation and transportation of sorbitol. In this study, the genome-wide identification of S6PDH, SDH and SOT genes was conducted in four Rosaceae species, peach, mei, apple and pear, and showed the sorbitol bio-pathway to be dominant (named sorbitol present group, SPG); another three related species, including tomato, poplar and Arabidopsis, showed a non-sorbitol bio-pathway (named sorbitol absent group, SAG). To understand the evolution- ary differences of the three important gene families between SAG and SPG, their corresponding gene duplication, evolutionary rate, codon bias and positive selection patterns have been analyzed and compared. The sorbitol path- way genes in SPG were found to be expanded through dispersed and tandem gene duplications. Branch-specific model analyses revealed SDH and S6PDH clade A were under stronger purifying selection in SPG. A higher frequency of optimal codons was found in S6PDH and SDH than that of SOT in SPG, confirming the purifying selection effect on them. In addition, branch-site model analyses revealed SOT genes were under positive selection in SPG. Expression analyses showed diverse expression patterns of sorbitol-related genes. Overall, these findings provide new insights in the evolutionary characteristics for the three key sorbitol metabolism-related gene families in Rosaceae and other non-sorbitol dominant pathway species

Genome-wide identification of the MADS-box transcription factor family in pear (Pyrus bretschneideri) reveals evolution and functional divergence

MADS-box transcription factors play significant roles in plant developmental processes such as floral organ conformation, flowering time, and fruit development. Pear (Pyrus), as the third-most crucial temperate fruit crop, has been fully sequenced. However, there is limited information about the MADS family and its functional divergence in pear. In this study, a total of 95 MADS-box genes were identified in the pear genome, and classified into two types by phylogenetic analysis. Type I MADS-box genes were divided into three subfamilies and type II genes into 14 subfamilies. Synteny analysis suggested that whole-genome duplications have played key roles in the expansion of the MADS family, followed by rearrangement events. Purifying selection was the primary force driving MADS-box gene evolution in pear, and one gene pairs presented three codon sites under positive selection. Full-scale expression information for PbrMADS genes in vegetative and reproductive organs was provided and proved by transcriptional and reverse transcription PCR analysis. Furthermore, the PbrMADS11(12) gene, together with partners PbMYB10 and PbbHLH3 was confirmed to activate the promoters of the structural genes in anthocyanin pathway of red pear through dual luciferase assay. In addition, the PbrMADS11 and PbrMADS12 were deduced involving in the regulation of anthocyanin synthesis response to light and temperature changes. These results provide a solid foundation for future functional analysis of PbrMADS genes in different biological processes, especially of pigmentation in pear