The mediator complex subunit PFT1 interferes with COP1 and HY5 in the regulation of Arabidopsis light signaling.

Arabidopsis (Arabidopsis thaliana) mutants hypersensitive to far-red light were isolated under a light program of alternating red and far-red light pulses and were named eid (for empfindlicher im dunkelroten Licht). The dominant eid3 mutant carries a missense mutation in a conserved domain of PHYTOCHROME AND FLOWERING TIME1 (PFT1), an important component of the plant mediator coactivator complex, which links promoter-bound transcriptional regulators to RNA polymerase II complexes. Epistatic analyses were performed to obtain information about the coaction between the mutated PFT1(eid3) and positively and negatively acting components of light signaling cascades. The data presented here provide clear evidence that the mutation mainly enhances light sensitivity downstream of phytochrome A (phyA) and modulates phyB function. Our results demonstrate that the Mediator component cooperates with CONSTITUTIVE PHOTORMORPHOGENIC1 in the regulation of light responses and that the hypersensitive phenotype strictly depends on the presence of the ELONGATED HYPOCOTYL5 transcription factor, an important positive regulator of light-dependent gene expression. Expression profile analyses revealed that PFT1(eid3) alters the transcript accumulation of light-regulated genes even in darkness. Our data further indicate that PFT1 regulates the floral transition downstream of phyA. The PFT1 missense mutation seems to create a constitutively active transcription factor by mimicking an early step in light signaling.

Are zinc levels in seminal plasma associated with seminal leukocytes and other determinants of semen quality?

OBJECTIVE: To evaluate a potential association of zinc levels with seminal leukocytes, the outcome of semen cultures; and semen quality and sperm fertilizing capacity. DESIGN: Prospective study. SETTING: Outpatient infertility clinic of a university hospital. PATIENT(S): Two hundred fifty-six randomly chosen asymptomatic males from subfertile couples. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Determination of zinc in seminal plasma by flame atomic absorption spectroscopy. In aliquots of the same ejaculates the following tests were performed: immunocytochemical round cell differentiation to determine leukocyte counts and ratios, microbial screening, and comprehensive evaluation of semen quality (sperm analysis, biochemical parameters, antisperm antibody testing, and in vitro examination of sperm ability to penetrate cervical mucus). The patients underwent medical history, clinical examination, and postcoital testing. Subsequent fertility was determined (controlled for female infertility factors). RESULT(S): The concentration of zinc in seminal plasma did not correlate in a statistically significant way with leukocytes in semen, nor was it associated with bacterial colonization. There was no statistically significant relationship of zinc in seminal plasma or serum with semen quality parameters nor with local antisperm antibody testing of the IgG or IgA class. Zinc levels did not influence sperm capacity to penetrate cervical mucus in vitro or in vivo, and did not affect subsequent fertility. CONCLUSION(S): The zinc level in seminal fluid and serum is not associated with silent male genital tract infection (indicated by seminal leukocytes); nor is it related to semen cultures in asymptomatic individuals. The lack of association with other semen quality parameters indicates that the routine determination of zinc levels during infertility investigation is not recommended.