Ascorbate peroxidase (APX) plays a key role in scavenging reactive oxygen species (ROS) in higher plants.  However, there is very little information available on the APXs in kiwifruit (Actinidia), which is an economically and nutritionally important horticultural crop with exceptionally high ascorbic acid (AsA) accumulation.  This study aims to identify and characterize two cytosolic APX genes (AcAPX1 and AcAPX2) derived from A. chinensis ‘Hongyang’.  The constitutive expression pattern was determined for both AcAPX1 and AcAPX2, and showed relatively higher expression abundances of AcAPX1 in leaf and AcAPX2 in root.  Transcript levels of AcAPX1 and AcAPX2 were increased in kiwifruit roots treated with NaCl.  Subcellular localization assays using GFP-fusion proteins in Arabidopsis protoplasts showed that both AcAPX1 and AcAPX2 are targeted to the cytosol.  Recombinant AcAPX1 or AcAPX2 proteins were successfully expressed in the prokaryotic expression system and their individual ascorbate peroxidase activities were determined.  Finally, constitutive over-expression of AcAPX1 or AcAPX2 could dramatically increase total AsA, glutathione level and salinity tolerance under NaCl stress in Arabidopsis thaliana.  Our findings revealed that cytosolic AcAPX1/2 may play an important protective role in the responses to unfavorable environmental stimuli in kiwifruit.

SOM encodes a nucleus-localized CCCH-type zinc finger protein and negatively regulates seed germination in Arabidopsis thaliana. We have previously demonstrated that ectopic expression of SlABI3, an important transcription factor in abscisic acid (ABA) signaling pathway, resulted in alteration of SlSOM expression patterns in both leaf and seed of tomato. In this study, we aimed to elucidate the function of tomato SlSOM in regarding to seed germination and seedling development. Here, we constructed SlSOM over-expression vector pBI121-SOM driven by CaMV 35S promoter, and the recombinant plasmid was incorporated into wild-type tomato by the method of Agrobacterium tumefaciens-mediated transformation. The result showed that over-expression of SlSOM conferred enhanced responses to exogenous ABA application during seed germination and seedling development. In addition, ectopic expression of SlSOM resulted in the alteration of expression level of ABA/GA (gibberellins) metabolic genes, such as SlABA1, SlCYP707A1, SlGA3ox2, and SlGA2ox4, in both leaf and seed. The ABA anabolic gene SlABA1 and the GA catabolic gene SlGA2ox4 were up-regulated while the ABA catabolic gene SlCYP707A1 and the GA anabolic gene SlGA3ox2 were down-regulated. Compared to wild type, the expression level of SlABI5 was increased by about 40–50% in transgenic seeds while adding exogenous ABA treatment. These results support the notion that SlSOM inhibits seed germination by regulating ABA/GA metabolic genes and SlABI5 expression in Solanum lycopersicum.

Ser/Arg-rich (SR) genes encode proteins that play pivotal roles in both constitutive and alternative splicing of pre-mRNA. However, not much effort has been made to investigate the alternative splicing of their own pre-mRNA. In this study, we conducted comprehensive analyses of pre-mRNA splicing for 22 SR genes in three rice (Oryza sativa L.) ecotypes indica, japonica and javanica. Using different ecotypes we characterized the variations in expression and splicing patterns of rice SR genes in different tissues and at different developmental stages. In addition, we compared the divergence in expression and splicing patterns of SR genes from seedlings of different rice ecotypes in response to hormones application and environmental stresses. Our results revealed the complexity of alternative splicing of SR genes in rice. The splicing varies in different tissues, in different ecotypes, in response to stresses and hormones. Thus, our study suggested that SR genes were subjected to sophisticated alternative splicing although their encoding proteins were involved in the splicing process.

The aldehyde dehydrogenase (ALDH) superfamily of NAD(P)+-dependent enzymes, in general, oxidize a wide range of endogenous and exogenous aliphatic and aromatic aldehydes to their corresponding carboxylic acids and play an essential role in detoxification of reactive oxygen species (ROS) accumulated under the stressed conditions. In order to identify genes required for the stresses responses in the grass crop Oryza sativa, a homologue of ALDH gene (OsALDH22) was isolated and characterized. OsALDH22 is conserved in eukaryotes, shares high homology with the orthologs from aldehyde dehydrogenase subfamily ALDH22. The OsALDH22 encodes a protein of 597 amino acids that in plants exhibit high identity with the orthologs from Zea mays, Sorghum bicolor, Hordeum vulgare and Arabidopsis thaliana, respectively, and the conserved amino acid characteristics for ALDHs are present, including the possible NAD+ binding site (F-V-G-SP- G-V-G), the catalytic site (V-T-L-E-L-G-G-K) and the Cys active site. Semi-quantitative PCR and real-time PCR analysis indicates that OsALDH22 is expressed differentially in different tissues. Various elevated levels of OsALDH22 expression have been detected when the seedlings exposed to abiotic stresses including dehydration, high salinity and abscisic acid (ABA). Transgenic rice plants overexpressing OsALDH22 show elevated stresses tolerance. On the contrary, downregulation of OsALDH22 in the RNA interference (RNAi) repression transgenic lines manifests declined stresses tolerance.