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Digital gene expression profiling technology was used to examine the changes in gene expression during floral transition in pak choi. A total of 1486 differentially expressed genes (DEGs) during floral transition were identified, of which 505 were upregulated and 981 were downregulated. Gene ontology enrichment analysis showed that the proteins encoded by DEGs were mainly located in eight cell regions including the apoplast, plant-type cell wall, chloroplast, etc. They had eight kinds of molecular functions such as transcription factor and oxidoreductase, and involved in 72 biological processes containing jasmonic acid and salicylic acid metabolism, glucose metabolism, the MAPK cascade, etc. Further pathway enrichment analysis showed that four metabolic pathways were significantly enriched by DEGs. DEGs that exhibited at least a 10-fold difference were analyzed in detail. Results showed that flavonoid metabolism and phenylpropanoid biosynthesis (or pathways) were significantly enriched and the corresponding gene number was the highest. Moreover, 15 genes among the highly expressed genes were involved in reproductive development, of which five homologues in Arabidopsis thalianawere directly related to floral transition, which were predicted to have a similar function in pak choi.

Flowering is critical to the growth and development of plants, and LFYgene homologues play a major role in flowering initiation. To understand the genetic and molecular mechanisms underlying floral initiation and development in Brassica rapasubsp. pekinensis, BrpLFY, a homologue of LFY, was cloned using RT-PCR. Sequence analysis showed that the cDNA sequence of BrpLFYis 1,341 bp in length, with an ORF of 1,245 bp encoding a predicted protein of 415 amino acids. The predicted protein showed a high degree of identity with LFY homologues from other angiosperm species. Real-time PCR analysis showed that BrpLFYmRNA was detected in all tissues during plant development from the vegetative state to fully differentiated flowers, and its expression was highest in the cotyledon and lowest in the root. BrpLFYexpression in the shoot apex increased gradually during vegetative growth and increased dramatically at stage 1 of flower bud differentiation. The relative expression peaked at stage 5 and then decreased in later stages. Moreover, the trend in BrpLFYexpression level change in the shoot apex was similar regardless of variety or vernalization method. The relative expression of BrpLFYin leaves gradually decreased with leaf development. We overexpressed the gene in Arabidopsis thalianausing the floral dip method, and examined flowering time in wild-type and transgenic plants. Overexpression of BrpLFYspecifically caused early flowering; the transgenic plants flowered 10-14 d earlier than did wild-type plants, and leaf number decreased by 0.5-1 when the plants bolted. Real-time PCR analysis showed that the expression of BrpLFYin transgenic Arabidopsis was higher than in wild-type plants. These results indicate that BrpLFYplays a role in promoting flowering in Chinese cabbage.

To study the resistant mechanism and clinical significance of pseudomonas aeruginosa toβ-lactam antibiotics, the outer membrane permeability rate of 30 P. aeruginosa strains to 5β-lactam antibiotics was measured and their production ofβ-lactamase and theβ-lactamase genes they carried detected. Furthermore, the relationship between the permeability,β-lactamase and the clinical effects ofβ-lactam antibiotics was observed. By using14C-penicillin and liquid-scintillant isotope assay, the affinity of penicillin binding proteins (PBPs) was measured and their roles in the resistant mechanism studied. It was revealed that the permeability rate was higher in sensitive strains than in resistant ones (P<0.05). All strains harbored 1–4β-lactamase genes and producedβ-lactamase. Higher permeability rate and higher degree of stability toβ-lactamase indicated better clinical therapeutic effects. The affinity of PBPs changed little without regard to the permeability andβ-lactamase. These results suggested that the permeability of outer membrane andβ-lactamase, but not PBPs, played important roles in the resistant mechanism of P. aeruginosa toβ-lactam antibiotics and affected the clinical therapeutic effectiveness of some patients.