Posttranscriptional control of gene expression can be achieved through RNA interference when the activities of Dicer-like (DCL), argonaute (AGO) and RNA-dependent RNA polymerase (RDR) proteins are significant. In this study, we analysed the expression of seven AGO, five DCL and eight RDR genes in cucumber under cold, heat, hormone, salinity and dehydration treatments using quantitative reverse-transcription PCR (qRT-PCR). All CsAGO, CsDCL and CsRDR genes were differentially expressed under abiotic stress treatment. In response to abiotic stress treatment, most genes were expressed at higher levels in flowers or stems than in other organs, whereas some CsAGOs (CsAGO1c, CsAGO6 and CsAGO7) and CsRDRs (CsRDR1d andCsRDR2) were highly expressed in roots during dehydration treatment. The expression patterns indicate that most CsDCLs, CsAGOs and CsRDRs respond to abiotic stress, and stems or flowers are the most sensitive organs, followed by roots. This is the first report of expression analysis of all CsDCL, CsAGO and CsRDR family genes in cucumber under abiotic stress, whichprovides basic information and insights into the putative roles of these genes in abiotic stress. The results of this study should serve as a basis for further functional characterization of these gene families in cucumber and related Cucurbitaceae species.

The receptor-like kinase ERECTA (ER) plays vital roles in plant adaptation under environmental stress including shade avoidance in Arabidopsis. In our previous study, we identified four ER paralogues in soybean (GmERs) that showed high similarities to Arabidopsis ER. Each GmER was predicted to generate diverse alternative splicing variants. However, whether soybean GmERs contribute to shade avoidance is unknown. Here we report our characterization of GmERs in response to shading. Promoter::GUS staining analysis shows that expression of GmER paralogous genes was differentially induced under shade stress. Further analyses show that GmERa.1 and GmERa.2 exhibit a larger distinction in length than the other GmER variants. GmERa.2 has the shortest length of amino acid with only 15 leucine-rich repeats which is the part of the extracellular domain of GmERa.1. Overexpression of GmERa.2 fully rescued the hypocotyl length, leaf area and petiole length, and the sensitivity of the hypocotyl of Arabidopsis mutant er-3 to shading, suggesting that the truncated extracellular domain of GmERa might contribute importantly to shade avoidance.

The hard clam (Meretrix petechialis) is a commercially important shellfish in China. To provide valuable insights into management and conservation of M. petechialis, we investigated the genetic variation and population structure of M. petechialis by analysing samples from nine geographical populations. In this study, the genetic diversity and differentiation of nine populations of M. petechialis were assessed using the mitochondrial cytochrome oxidase subunit I (mtCOI) gene. A total of 90 COI sequences were obtained and each COI sequence was 699 bp in length. Fifty-one haplotypes were identified with 10 haplotypes sharedamong populations. The haplotype diversity was highest in Fujian, Panjin and Jiangsu (0.9778 ± 0.0540) and lowest in Dalian (0.7778 ± 0.1374). The nucleotide diversity was highest in Panjin (0.453401 ± 0.240463) and lowest in Jiangsu (0.006213 ± 0.004141). Neutral test (Fu’s Fs) and mismatch distribution analysis revealed that the hard clam experienced a population expansion event. Analysis of molecular variance (AMOVA) indicated that 91.7% of the genetic variance was within populations and 0.52% of the variance was among populations, demonstrating significant genetic differentiation among populations (P < 0.05). The neighbour-joining tree showed that the haplotypes were not clustered according to the geographical location, but some haplotypes from the same or neighbouring locations grouped together. The results obtained in this study provide useful information on the genetic diversity and population structure of M. petechialis and shed light on the management and protection of resources of M. petechialis in the northwestern Pacific.