By employing TCLs (thin cell layers) culture, the floral gradient in flowering tobacco of different developmental stages was confirmed. The TCLs from early flowering tobacco regenerated more floral buds than those fro...By employing TCLs (thin cell layers) culture, the floral gradient in flowering tobacco of different developmental stages was confirmed. The TCLs from early flowering tobacco regenerated more floral buds than those from the tobacco plants in full blooming or fruiting stages. Analysis of free amino acid levels revealed the acropetal gradient of Pro in flowering tobacco stem. L-Pro. L-Trp. D,L-Met and L-Arg were respectively added into the culture medium for testing their influence on floral bud formation from tobacco pedicel segments. Only L-Trp evidently enhanced the floral bud neoformation.展开更多
YfiBNR is a recently identified bis-（3＇-5＇）-cyclic dimeric GMP （c-di-GMP） signaling system in opportunistic pathogens. It is a key regulator of biofilm formation, which is correlated with prolonged persistence o...YfiBNR is a recently identified bis-（3＇-5＇）-cyclic dimeric GMP （c-di-GMP） signaling system in opportunistic pathogens. It is a key regulator of biofilm formation, which is correlated with prolonged persistence of infection and antibiotic drug resistance. In response to cell stress, YfiB in the outer membrane can sequester the pariplasmic protein YfiR, releasing its inhibition of YfiN on the inner membrane and thus provoking the diguanylate cyclase activity of YfiN to induce c-di-GMP production. However, the detailed regulatory mechanism remains elusive. Here, we report the crystal struc- tures of YfiB alone and of an active mutant YfiB^L43P complexed with YfiR with 2：2 stoichiometry. Structural analyses revealed that in contrast to the compact conformation of the dimeric YfiB alone, YfiB^L43P adopts a stretched conformation allowing activated YfiB to penebate the peptidoglycan （PG） layer and access YfiR. YfiBL43P shows a more compact PG-binding pocket and much higher PG binding affinity than wild-type YflB, suggesting a tight correlation between PG binding and YfiB activation. In addition, our crystallographic analyses revealed that YflR binds Vitamin B6 （VB6） or L-Trp at a YfiB-binding site and that both VB6 and L-Trp are able to reduce YfiBL43P-induced biofilm formation. Based on the structural and biochemical data, we propose an updated regulatory model of the YfiBNR system.展开更多
文摘By employing TCLs (thin cell layers) culture, the floral gradient in flowering tobacco of different developmental stages was confirmed. The TCLs from early flowering tobacco regenerated more floral buds than those from the tobacco plants in full blooming or fruiting stages. Analysis of free amino acid levels revealed the acropetal gradient of Pro in flowering tobacco stem. L-Pro. L-Trp. D,L-Met and L-Arg were respectively added into the culture medium for testing their influence on floral bud formation from tobacco pedicel segments. Only L-Trp evidently enhanced the floral bud neoformation.
文摘YfiBNR is a recently identified bis-（3＇-5＇）-cyclic dimeric GMP （c-di-GMP） signaling system in opportunistic pathogens. It is a key regulator of biofilm formation, which is correlated with prolonged persistence of infection and antibiotic drug resistance. In response to cell stress, YfiB in the outer membrane can sequester the pariplasmic protein YfiR, releasing its inhibition of YfiN on the inner membrane and thus provoking the diguanylate cyclase activity of YfiN to induce c-di-GMP production. However, the detailed regulatory mechanism remains elusive. Here, we report the crystal struc- tures of YfiB alone and of an active mutant YfiB^L43P complexed with YfiR with 2：2 stoichiometry. Structural analyses revealed that in contrast to the compact conformation of the dimeric YfiB alone, YfiB^L43P adopts a stretched conformation allowing activated YfiB to penebate the peptidoglycan （PG） layer and access YfiR. YfiBL43P shows a more compact PG-binding pocket and much higher PG binding affinity than wild-type YflB, suggesting a tight correlation between PG binding and YfiB activation. In addition, our crystallographic analyses revealed that YflR binds Vitamin B6 （VB6） or L-Trp at a YfiB-binding site and that both VB6 and L-Trp are able to reduce YfiBL43P-induced biofilm formation. Based on the structural and biochemical data, we propose an updated regulatory model of the YfiBNR system.
