HOS15 represses flowering by promoting GIGANTEA degradation in response to low temperature in Arabidopsis

Flowering is the primary stage of the plant developmental transition and is tightly regulated by environmental factors such as light and temperature.However,the mechanisms by which temperature signals are integrated into the photoperiodic flowering pathway are still poorly understood.Here,we demonstrate that HOS15,which is known as a GI transcriptional repressor in the photoperiodic flowering pathway,controls flowering time in response to low ambient temperature.At 16℃,the hos15 mutant exhibits an early flowering phenotype,and HOS15 acts upstream of photoperiodic flowering genes(GI,CO,and FT).GI protein abundance is increased in the hos15 mutant and is insensitive to the proteasome inhibitor MG132.Furthermore,the hos15 mutant has a defect in low ambient temperature-mediated GI degradation,and HOS15 interacts with COP1,an E3 ubiquitin ligase for GI degradation.Phenotypic analyses of the hos15 cop1 double mutant revealed that repression of flowering by HOS15 is dependent on COP1 at 16℃.However,the HOS15-COP1 interaction was attenuated at 16℃,and GI protein abundance was additively increased in the hos15 cop1 double mutant,indicating that HOS15 acts independently of COP1 in GI turnover at low ambient temperature.This study proposes that HOS15 controls GI abundance through multiple modes as an E3 ubiquitin ligase and transcriptional repressor to coordinate appropriate flowering time in response to ambient environmental conditions such as temperature and day length.

Redox sensor QSOX1 regulates plant immunity by targeting GSNOR to modulate ROS generation

Reactive oxygen signaling regulates numerous biological processes,including stress responses in plants.Redox sensors transduce reactive oxygen signals into cellular responses.Here,we present biochemical evidence that a plant quiescin sulfhydryl oxidase homolog(QSOX1)is a redox sensor that negatively regulates plant immunity against a bacterial pathogen.The expression level of QSOX1 is inversely correlated with pathogen-induced reactive oxygen species(ROS)accumulation.Interestingly,QSOX1 both senses and regulates ROS levels by interactingn with and mediating redox regulation of S-nitrosoglutathione reductase,which,consistent with previous findings,influences reactive nitrogen-mediated regulation of ROS generation.Collectively,our data indicate that QSOX1 is a redox sensorthat negatively regulates plant immunity by linking reactive oxygen and reactive nitrogen signaling to limit ROS production.

Plant-based,adjuvant-free,potent multivalent vaccines for avian influenza virus via Lactococcus surface display

Influenza epidemics frequently and unpredictably break out all over the world,and seriously affect the breeding industry and human activity.Inactivated and live attenuated viruses have been used as protective vaccines but exhibit high risks for biosafety.Subunit vaccines enjoy high biosafety and specificity but have a few weak points compared to inactivated virus or live attenuated virus vaccines,especially in low immunogenicity.In this study,we developed a new subunit vaccine platform for a potent,adjuvant-free,and multivalent vaccination.The ectodomains of hemagglutinins(HAs)of influenza viruses were expressed in plants as trimers(tHAs)to mimic their native forms.tHAs in plant extracts were directly used without purification for binding to inactivated Lactococcus(iLact)to produce iLact-tHAs,an antigen-carrying bacteria-like particle(BLP).tHAs BLP showed strong immune responses in mice and chickens without adjuvants.Moreover,simultaneous injection of two different antigens by two different formulas,t^(HAH5N6+H9N2) BLP or a combination of t^(HAH5N6) BLP and t^(HAH9N2) BLP,led to strong immune responses to both antigens.Based on these results,we propose combinations of plant-based antigen production and BLP-based delivery as a highly potent and cost-effective platform for multivalent vaccination for subunit vaccines.