ZTL regulates thermomorphogenesis through TOC1 and PRR5.

Plants adapt to high temperature stresses through thermomorphogenesis, a process that includes stem elongation and hyponastic leaf growth. Thermomorphogenesis is gated by the circadian clock through two evening-expressed clock components, TIMING OF CAB EXPRESSION1 (TOC1) and PSEUDO-RESPONSE REGULATORS5 (PRR5). These proteins directly interact with and inhibit PHYTOCHROME INTERACTING FACTOR4 (PIF4), a basic helix-loop-helix transcription factor that promotes thermoresponsive growth. PIF4-mediated thermoresponsive growth is positively regulated by ZEITLUPE (ZTL), a central clock component, but the molecular mechanisms underlying this are poorly understood. Here, we show that ZTL regulates thermoresponsive growth through TOC1 and PRR5. Genetic analyses reveal that ZTL regulates PIF4 activity as well as PIF4 expression. In Arabidopsis thaliana, ztl mutants exhibit highly accumulated TOC1 and PRR5 and unresponsive expression of PIF4 target genes under exposure to high temperatures. Mutations in TOC1 and PRR5 restore thermoactivation of PIF4 target genes and thermoresponsive growth in ztl mutants. We also show that the molecular chaperone heat-shock protein 90 promotes thermoresponsive growth through the ZTL-TOC1/PRR5 signaling module. Further, we show that ZTL protein stability is increased at high temperatures. Taken together, our results demonstrate that ZTL-mediated degradation of TOC1 and PRR5 enhances the sensitivity of hypocotyl growth to high temperatures.

Overexpression of BBX18 Promotes Thermomorphogenesis Through the PRR5-PIF4 Pathway.

Thermomorphogenesis is the morphological response of plants to an elevation in the ambient temperature, which is mediated by the bHLH transcription factor PIF4. The evening-expressed clock component, PRR5, directly represses the expression of PIF4 mRNA. Additionally, PRR5 interacts with PIF4 protein and represses its transactivation activity, which in turn suppresses the thermoresponsive growth in the evening. Here, we found that the B-box zinc finger protein, BBX18, interacts with PRR5 through the B-Box2 domain. Deletion of the B-Box2 domain abolished the functions of BBX18, including the stimulation of PIF4 mRNA expression and hypocotyl growth. Overexpression of BBX18, and not of B-Box2-deleted BBX18, restored the expression of thermoresponsive genes in the evening. We further show that BBX18 prevents PRR5 from inhibiting PIF4-mediated high temperature responses. Taken together, our results suggest that BBX18 regulates thermoresponsive growth through the PRR5-PIF4 pathway.

Prevalence of Chlamydia trachomatis and Neisseria gonorrhoeae in an urban public hospital pregnancy termination clinic.

This study is a follow-up observational study to assess the prevalence of chlamydia (CT) and gonorrhea (GC) among women who undergo a first-trimester surgical termination in a large public, urban hospital-based termination clinic, and to compare the rates to previously published data. We conducted a retrospective chart review on 4197 patients who underwent CT and GC testing before an elective, first-trimester surgical termination between 1 June 2014 and 31 May 2015. The prevalence rates were calculated and compared by chi square tests to previously published data from 1 January 2006 to 30 June 2006 from the same publicly-funded pregnancy termination clinic. Our study population comprised mostly of African Americans (86.8%), and more than half were aged less than 25 years. The overall prevalence of CT in our population was 9.6%, which was significantly different to the prevalence of 11.4% in 2006 ( p value = 0.03). The overall prevalence of GC in our population was 1.9%, which was not significantly different to the prevalence of 2.6% in 2006. To conclude, this study demonstrates the high prevalence rate of CT-positive and GC-positive patients in our publicly-funded pregnancy termination clinic. The prevalence of infection with CT and GC in our study is higher than in other family planning clinics. Regular screening of all patients who undergo induced termination in pregnancy termination clinics can provide a valuable opportunity for physicians to counsel patients about sexually transmitted infection prevention and treatment prior to the procedure or distribution of medications.