CloudChord: A P2P Network of Clients Cloud Storage for Data Access Pattern Privacy

Cloud storage is becoming more and more popular in recent years. Users can use cloud storage services without investing a large amount of money to set up and maintain their own storage systems. However, cloud storage servers cannot be fully trusted. Although encryption of data provides a partial solution to the problem, it is still possible that a server can learn some information about a user based on the user’s access pattern, and further predicts the user’s activities. In this project, we aim to build a distributed system in the users’ side to hide the users’ access patterns from a server. Our design is based on the idea that, by mixing the accesses from a large number of active users, each individual user’s access pattern can be easily buried among the collective access patterns of all the users. Especially, we develop a P2P network system called CloudChord that integrates the cloud storages of a set of users. With CloudChord, file blocks of each individual user can migrate to the cloud storages of other users in the set, so that the user’s access pattern is hidden from the server. CloudChord is designed to run in the users’ premise to protect the data privacy of the users without the involvement of the server. CloudChrod also aims to provide a higher level of data security, availability and fairness for all the users

Investigating the roles of diterpenoids in rice-Xanthomonas oryzae interactions

Secondary metabolites play a significant role in mediating plant-microbe interactions. Rice (Oryza sativa) is one of the most important staple crops. Once rice is attacked by microbial pathogens, it will produce phytoalexins antibiotics to defend against enemies such as the bacterial pathogen Xanthomonas oryzae. Diterpenoids provide a rich source of metabolites mediating rice-X. oryzae interaction. First, gibberellin (GA), as complex diterpenoid phytohormone, besides the profound effects on plant growth and development, it has been shown to negatively regulate rice defense. Interestingly, we found a putative GA biosynthetic gene operon in rice bacterial leaf streak pathogen Xanthomonas oryzae pv. oryzicola (Xoc). Based on this, we biochemically characterized Xoc for its capacity to produce the precursor of GA. With genome mining, we found three other genera of rhizobia contained homologous GA biosynthetic gene operon and shared the identical biochemical function for production of ent-kaurene. As for Xoc, we detected the putative production of GA was relevant to virulence ability in Xoc through antagonism to jasmonic acid. The role of putative GA diterpenoid regulated Xoc\u27s association with rice. Second, rice produces an arsenal of phytoalexins as responses to fungal and bacterial infection. Most of the known rice phytoalexins are diterpenoids. The relevance of these diterpenoids to defense was evaluated based on their antibiotic activity in vitro; the physiological role in planta remains undefined. Rice diterpenoids phytoalexins biosynthesis proceeds ent-copalyl diphosphate synthase (OsCPS2) or syn-copalyl diphosphate synthase (OsCPS4) from diterpenoid precursor geranylgeranyl diphosphate (GGPP). With reverse genetics approach we found the relevance of rice diterpenoids to defense depends on OsCPS2 pathway instead of OsCPS4. Furthermore, with application of CRISPR/Cas9 genome editing technology, I not only explored the relevance of the specific diterpenoid pathway downstream of OsCPS2 to rice plant defense but identified the redirection of metabolites levels in rice specialized metabolism as well. These results will not only elucidate some insight into the metabolites balance in rice-X. oryzae interaction but also provide the potential agricultural application for molecular breeding