Orchidaceae, renowned for its spectacular flowers and other reproductive and ecological adaptations, is one of the most diverse plant families. Here we present the genome sequence of the tropical epiphytic orchid Phalaenopsis equestris, a frequently used parent species for orchid breeding. P. equestris is the first plant with crassulacean acid metabolism (CAM) for which the genome has been sequenced. Our assembled genome contains 29,431 predicted protein-coding genes. We find that contigs likely to be underassembled, owing to heterozygosity, are enriched for genes that might be involved in self-incompatibility pathways. We find evidence for an orchid-specific paleopolyploidy event that preceded the radiation of most orchid clades, and our results suggest that gene duplication might have contributed to the evolution of CAM photosynthesis in P. equestris. Finally, we find expanded and diversified families of MADS-box C/D-class, B-class AP3 and AGL6-class genes, which might contribute to the highly specialized morphology of orchid flowers

Akt is a protein serine/threonine kinase that is involved in the regulation of diverse cellular processes. Phosphorylation of Akt at regulatory residues Thr-308 and Ser-473 leads to its full activation. The protein phosphatase 2A (PP2A) has long been known to negatively regulate Akt activity. The PP2A holoenzyme consists of the structural subunit (A), catalytic subunit (C), and a variable regulatory subunit (B). Here we report the identification of the specific B regulatory subunit that targets the PP2A holoenzyme to Akt. We found endogenous association of PP2A AB55C holoenzymes with Akt by co-immunoprecipitation analyses in pro-lymphoid FL5.12 cells. Akt was shown to associate with ectopically expressed B55␣ subunit in NIH3T3 cells. The direct interaction between B55␣ subunit and Akt was confirmed using in vitro pulldown analyses. Intriguingly, we found that overexpression of B55␣ subunit significantly impaired phosphorylation at Thr-308, but to a lesser extent at Ser-473 of Akt in both FL5.12 and NIH3T3 cells. Concomitantly, phosphorylation of a subset of Akt substrates, including FoxO3a, was substantially decreased by B55␣ overexpression in these cells. Silencing of B55␣ expression markedly increased phosphorylation at Thr-308 but not at Ser-473 in both FL5.12 cells and NIH3T3 cells. Consistently, PP2A AB55␣C holoenzymes preferentially dephosphorylated phospho-Thr-308 rather than phospho-Ser-473 in in vitro dephosphorylation assays. Furthermore, B55␣ overexpression retarded proliferation of NIH3T3 cells, and knockdown of B55␣ expression increased survival of FL5.12 cells upon interleukin-3 deprivation. Together, our data demonstrate that B55␣-dependent targeting of the PP2A holoenzyme to Akt selectively regulates Akt phosphorylation at Thr-308 to regulate cell proliferation and survival.

Three derivatives of poly(paraphenylene) (PPP) have been synthesized, all with excellent solubility in common organic solvents. Efficient blue polymer light-emitting diodes (LEDs) are demonstrated using these PPPs as the semiconducting and luminescent polymers. Double-layer polymer LEDs (consisting of a hole transport layer in addition to the electroluminescent layer) emit blue light with external quantum efficiencies between 1% and 3% photons per electron, when using indium tin oxide as the anode and calcium as the cathode. Using internal field emission (Fowler–Nordheim tunneling) of single carrier devices for both electrons and holes, the energies of the top of the π band and the bottom of the π* band have been determined as, respectively, 5.7 and 2.3 eV below the vacuum. The operating voltages of these LEDs have been lowered by using a porous polyaniline anode, or by blending PPP with a hole transport material. LEDs using air stable cathodes, silver, indium, aluminum, and copper, were also demonstrated. Device quantum efficiencies, between 0.3% and 0.8%, were obtained.

We demonstrate that by using polyaniline (PANI) or a combination of (PANI) and indium/tin oxide (ITO) as the transparent anode of a polymer light-emitting diode with poly[2-methoxy-5-(2′-ethyl- hexyloxy)-1,4-phenylene vinylene] (MEH-PPV), as the active layer, device performance can be significantly improved. The operating voltage can be reduced by ∼30%–50% and the quantum efficiency can be increased by ∼30%–40% with respect to the devices using ITO alone as the hole-injecting anode. The barrier height at the PANI/MEH-PPV interface is estimated to be ∼0.08–0.12 eV, approximately half of that at the ITO/MEH-PPV interface.

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