VcMYB4a, an R2R3-MYB transcription factor from Vaccinium corymbosum, negatively regulates salt, drought, and temperature stress.

MYB transcription factors (TFs) play important roles in the plant's response to abiotic stress. In this study, we cloned a novel MYB TF gene from Vaccinium corymbosum (blueberry) using rapid amplification of cDNA ends (RACE). The cDNA contained a 798-bp open reading frame that encodes a 265-amino acid protein. VcMYB4a possessed a C2/EAR-repressor motif domain and phylogenetic analysis showed that it clustered into a subgroup 4 with six Arabidopsis thaliana MYBs. Quantitative RT-PCR analysis demonstrated that VcMYB4a expression was downregulated by salt, drought, and cold treatment, but was induced by freezing and heat. Overexpression of VcMYB4a in blueberry callus enhanced sensitivity to salt, drought, cold, freezing, and heat stress. These results indicate that VcMYB4a may be an important repressor of abiotic stress in blueberry.

Ultrahigh-performance transparent conductive films of carbon-welded isolated single-wall carbon nanotubes.

Single-wall carbon nanotubes (SWCNTs) are ideal for fabricating transparent conductive films because of their small diameter, good optical and electrical properties, and excellent flexibility. However, a high intertube Schottky junction resistance, together with the existence of aggregated bundles of SWCNTs, leads to a degraded optoelectronic performance of the films. We report a network of isolated SWCNTs prepared by an injection floating catalyst chemical vapor deposition method, in which crossed SWCNTs are welded together by graphitic carbon. Pristine SWCNT films show a record low sheet resistance of 41 ohm □-1 at 90% transmittance for 550-nm light. After HNO3 treatment, the sheet resistance further decreases to 25 ohm □-1. Organic light-emitting diodes using this SWCNT film as anodes demonstrate a low turn-on voltage of 2.5 V, a high current efficiency of 75 cd A-1, and excellent flexibility. Investigation of isolated SWCNT-based field-effect transistors shows that the carbon-welded joints convert the Schottky contacts between metallic and semiconducting SWCNTs into near-ohmic ones, which significantly improves the conductivity of the transparent SWCNT network. Our work provides a new avenue of assembling individual SWCNTs into macroscopic thin films, which demonstrate great potential for use as transparent electrodes in various flexible electronics.

Organic semiconductor heterojunctions: electrode-independent charge injectors for high-performance organic light-emitting diodes.

Organic light-emitting diodes (OLEDs) are driven by injected charges from an anode and a cathode. The low and high work function metals are necessary for the effective injection of electrons and holes, respectively. Here, we introduce a fully novel design concept using organic semiconductor heterojunctions (OSHJs) as the charge injectors for achieving highly efficient OLEDs, regardless of the work functions of the electrodes. In contrast to traditional injected charges from the electrodes, the injected charges originate from the OSHJs. The device performance was shown to be significantly improved in efficiency and stability compared to conventional OLEDs. Attractively, the OLEDs based on OSHJs as charge injectors still exhibited an impressive performance when the low work function Al was replaced by air- and chemistry-stable high work function metals, such as Au, Ag, and Cu, as the cathode contact, which has been suggested to be difficult in conventional OLEDs. This concept challenges the conventional design approach for the injection of charges and allows for the realization of practical applications of OLEDs with respect to high efficiency, selectable electrodes, and a long lifetime.