Alzheimer's disease is characterized by cerebral deposits of amyloid beta-protein (AP) as senile plaque core and vascular amyloid, and a complementary DNA encoding a precursor of this protein (APP) has been cloned from human brain. From a cDNA library of a human glioblastoma cell line, we have isolated a cDNA identical to that previously reported, together with a new cDNA which contains a 225-nucleotide insert. The sequence of the 56 amino acids at the N-terminal of the protein deduced from this insert is highly homologous to the basic trypsin inhibitor family, and the lysate from COS-1 cells transfected with the longer APP cDNA showed an increased inhibition of trypsin activity. Partial sequencing of the genomic DNA encoding APP showed that the 225 nucleotides are located in two exons. At least three messenger RNA species, apparently transcribed from a single APP gene by alternative splicing, were found in human brain. We suggest that protease inhibition by the longer APP(s) could be related to aberrant APP catabolism.

Rice is a facultative short-day plant, and molecular genetic studies have identified the major genes involved in short-day flowering. However, the molecular mechanisms promoting the diversity of flowering time in cultivated rice are not known. We used a core collection of 64 rice cultivars that represent the genetic diversity of 332 accessions from around the world and studied the expression levels and polymorphisms of 6 genes in the short-day flowering pathway. The RNA levels of Heading date 3a (Hd3a), encoding a floral activator, are highly correlated with flowering time, and there is a high degree of polymorphism in the Heading date 1 (Hd1) protein, which is a major regulator of Hd3a expression. Functional and nonfunctional alleles of Hd1 are associated with early and late flowering, respectively, suggesting that Hd1 is a major determinant of variation in flowering time of cultivated rice. We also found that the type of Hd3a promoter and the level of Ehd1 expression contribute to the diversity in flowering time and Hd3a expression level. We evaluated the contributions of these 3 factors by a statistical analysis using a simple linear model, and the results supported our experimental observations.) has evolved during the last 8,000 to 10,000 years of domestication and breeding (1, 2). A major reason for the spread of rice cultivation to a wide range of geographical regions, and for the increases in yield, is the diversification of flowering time (1). In general, rice is known as a short-day plant that induces transition from the vegetative phase to the reproductive phase when it senses a decrease in day length. The molecular genetic pathway for short-day flowering in cultivated rice (Fig. 1A) is relatively well characterized (3-5). Signals from light and circadian clocks are received by OsGI, the rice orthologue of Arabidopsis GIGANTEA, and it regulates expression of Heading date 1 (Hd1) and OsMADS51 (6-8). Hd1 and its Arabidopsis orthologue CONSTANS encode zinc-finger type transcriptional activators with the CO, CO-like, and TOC1 (CCT) domains (9). Hd1 regulates Heading date 3a (Hd3a) expression (7, 9, 10). Hd3a is a rice orthologue of Arabidopsis FLOWERING LOCUS T (FT), and these genes recently were shown to encode a mobile flowering signal (11-16). RICE FLOWERING LOCUS T1 (RFT1) belongs to the rice FT-like gene family and functions as a floral activator, acting redundantly with Hd3a (17, 18). OsMADS51 encodes a type I MADSbox gene and functions upstream of Early heading date 1 (Ehd1) (8). Ehd1 encodes a B-type response regulator and acts as an activator of Hd3a independently from Hd1 (19). No clear orthologues of Ehd1 or OsMADS51 are found in the Arabidopsis genome. Although the genetic pathway for short-day flowering in rice is relatively well understood, the molecular mechanisms generating the diversity of flowering time in cultivated rice are not known. In this study, we analyzed the expression and nucleotide sequences of genes involved in short-day flowering in rice. Our study revealed that allelic vari...

Three triphenyl benzene derivatives of 1,3,5‐tri(m‐pyrid‐2‐yl‐phenyl)benzene (Tm2PyPB), 1,3,5‐tri(m‐pyrid‐3‐yl‐phenyl)benzene (Tm3PyPB) and 1,3,5‐tri(m‐pyrid‐4‐yl‐phenyl)benzene (Tm4PyPB), containing pyridine rings at the periphery, are developed as electron‐transport and hole/exciton‐blocking materials for iridium(III) bis(4,6‐(di‐fluorophenyl)pyridinato‐N,C2′)picolinate (FIrpic)‐based blue phosphorescent organic light‐emitting devices. Their highest occupied molecular orbital and lowest unoccupied molecular orbital (LUMO) energy levels decrease as the nitrogen atom of the pyridine ring moves from position 2 to 3 and 4; this is supported by both experimental results and density functional theory calculations, and gives improved electron‐injection and hole‐blocking properties. They exhibit a high electron mobility of 10−4–10−3 cm2 V−1 s−1 and a high triplet energy level of 2.75 eV. Confinement of FIrpic triplet excitons is strongly dependent on the nitrogen atom position of the pyridine ring. The second exponential decay component in the transient photoluminescence decays of Firpic‐doped films also decreases when the position of the nitrogen atom in the pyridine ring changes. Reduced driving voltages are obtained when the nitrogen atom position changes because of improved electron injection as a result of the reduced LUMO level, but a better carrier balance is achieved for the Tm3PyPB‐based device. An external quantum efficiency (EQE) over 93% of maximum EQE was achieved for the Tm4PyPB‐based device at an illumination‐relevant luminance of 1000 cd m−2, indicating reduced efficiency roll‐off due to better confinement of FIrpic triplet excitons by Tm4PyPB in contrast to Tm2PyPB and Tm3PyPB.

SUMMARYPlants detect changes in day length to induce seasonal patterns of flowering. The photoperiodic pathway accelerates the flowering of Arabidopsis thaliana under long days (LDs) whereas it is inactive under short days (SDs), resulting in delayed flowering. This delay is overcome by exposure of plants to high temperature (27°C) under SDs (27°C-SD). Previously, the high-temperature flowering response was proposed to involve either the impaired activity of MADS-box transcription factor (TF) floral repressors or PHYTO-CHROME-INTERACTING FACTOR 4 (PIF4) TF-mediated activation of FLOWERING LOCUS T (FT), which encodes the output signal of the photoperiodic pathway. We integrate these observations by studying several PIFs, the MADS-box SHORT VEGETATIVE PHASE (SVP) and the photoperiodic pathway under 27°C-SD. We find that the mRNAs of FT and its paralogue TWIN SISTER OF FT (TSF) are increased at dusk under 27°C-SD compared with 21°C-SD, and that this requires PIF4 and PIF5 as well as CONSTANS (CO), a TF that promotes flowering under LDs. The CO and PIF4 proteins are present at dusk under 27°C-SD, and they physically interact. Although Col-0 plants flower at similar times under 27°C-SD and 21°C-LD the expression level of FT is approximately 10-fold higher under 21°C-LD, suggesting that responsiveness to FT is also increased under 27°C-SD, perhaps as a result of the reduced activity of SVP in the meristem. Accordingly, only svp-41 ft-10 tsf-1 plants flowered at the same time under 21°C-SD and 27°C-SD. Thus, we propose that under non-inductive SDs, elevated temperatures increase the activity and sensitize the response to the photoperiod pathway.

SummaryPlants monitor and integrate temperature, photoperiod and light quality signals to respond to continuous changes in their environment. The GIGANTEA (GI) protein is central in diverse signaling pathways, including photoperiodic, sugar and light signaling pathways, stress responses and circadian clock regulation. Previously, GI was shown to activate expression of the key floral regulators CONSTANS (CO) and FLOWERING LOCUS T (FT) by facilitating degradation of a family of CYCLING DOF FACTOR (CDF) transcriptional repressors. However, whether CDFs are implicated in other processes affected by GI remains unclear. We investigated the contribution of the GI–CDF module to traits that depend on GI. Transcriptome profiling indicated that mutations in GI and the CDF genes have antagonistic effects on expression of a wider set of genes than CO and FT, whilst other genes are regulated by GI independently of the CDFs. Detailed expression studies followed by phenotypic assays showed that the CDFs function downstream of GI, influencing responses to freezing temperatures and growth, but are not necessary for proper clock function. Thus GI‐mediated regulation of CDFs contributes to several processes in addition to flowering, but is not implicated in all of the traits influenced by GI.