SQUAMOSA Promoter-Binding Protein-Like (SPL) genes encode plant-specific transcription factors that play important roles in plant phase transition, flower and fruit development, plant architecture, gibberellins signaling, sporogenesis, and response to copper and fungal toxins. In Arabidopsis, many SPL genes are post-transcriptionally regulated by the microRNA (miRNA) miR156, among which AtSPL9 in turn positively regulates the expression of the second miRNA miR172. This miR156-AtSPL9-miR172 regulatory pathway plays critical roles during juvenile to adult leaf development and the miR156-SPLs feedback interaction persists all through the plant development, which may be conserved in other plants. In the present paper, we provide a concise review on the most recent progress in the regulatory mechanisms associated with plant SPL transcription factors, especially in relation to miRNAs. The potential application of these discoveries in agriculture is briefly discussed.

In planta RNAi (i.e. plants engineered to synthesize active RNAi molecules) has great potential as a strategy to control insect crop pests. This study investigated the impact of RNAi against osmoregulatory genes expressed in the gut of two phloem-feeding species, the green peach aphid Myzus persicae and the potato/tomato psyllid Bactericera cockerelli. The target genes comprising candidate gut sucrase, aquaporin and sugar transporter genes were identified by mining insect genomic and transcriptomic datasets for genes orthologous to empirically-tested osmoregulatory genes of the pea aphid Acyrthosiphon pisum. Insects feeding on plants with RNAi against the target genes exhibited elevated hemolymph osmotic pressure (a predicted effect of perturbed osmotic function) and some reduction in performance, especially offspring production in M. persicae and mortality in B. cockerelli, associated with up to 50% reduction in mean expression of the target genes. The effects were particularly pronounced for insects treated with RNAi against multiple osmoregulatory genes, i.e. combinatorial RNAi, suggesting that the partial silencing of multiple genes with related roles can yield greater functional impairment than RNAi against a single gene. These results demonstrate the potential of RNAi against osmoregulatory genes, but further advances to improve the efficacy of RNAi in phloem-feeding insects are required to achieve effective pest control.

Determination of an optimal number/set of endogenous control (EC) microRNA (miRNA) genes is a critical but often an underappreciated aspect of quantitative gene expression analysis. In this study, the expression stabilities of 13 selected porcine EC miRNA genes were compared in all 47 tissue-specific normal tissues, 10 types of adipose tissue, and four types of muscle tissue using an EvaGreen quantitative PCR approach. Seven, 12, and 11 genes exhibited credible stability in the three groups, respectively. Our analysis clearly showed that three optimal EC genes are adequate for an accurate normalization, which correlated well with the theoretical optimal number (r ≥ 0.841). In terms of economical and experimental feasibility, we recommend the use of the three most stable EC miRNA genes for calculating the normalization factor, that is, ssc-miR-17, -103 and -107 for all 47 different tissues. We also suggest that two sets of EC miRNA genes are appropriate for 10 types of adipose tissue (ssc-miR-17, -107 and -24) and four types of muscle tissue (ssc-miR-17, -23a and -103), respectively. We envision that these results will serve as a valuable reference for other studies aimed at measuring tissue-specific miRNA abundance in porcine samples.

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