Barley aleurone layer cell protoplasts as a transient expression system

An effector-reporter system to study cellular signal transduction in strawberry fruit (Fragaria ananassa)

An effector-reporter system is a powerful tool used to study cellular signal transduction, but this technique has been traditionally used in protoplasts. A similar system to study cellular signal transduction in fruits has not yet been established. In this study, we aimed to establish an effector-reporter system for strawberry fruit, a model nonclimacteric fruit. We first investigated the characteristics of transient gene expression in strawberry fruits and found marked variation in gene expression levels among individual fruits, and this variation has complicated the establishment of a technical system. To overcome this difficulty, we investigated a sampling strategy based on a statistical analysis of the activity pattern of four different reporters (GUS, GFP, FLuc, and RLuc) among individual fruits and combinations of pairs of reporters (GUS/GFP and RLuc/FLuc). Based on an optimized sampling strategy, we finally established a step-by step protocol for the effector/reporter assay. Using FaMYB10 and FaWRKY71 as the effectors and GUS driven by the FaCHS promoter as the reporter, we demonstrated that this effector/reporter system was practical and reliable. This effector/reporter technique will contribute to an in-depth exploration of the signaling mechanism for the regulation of strawberry fruit ripening.

Epitope-tagged protein-based artificial miRNA screens for optimized gene silencing in plants

Artificial miRNA (amiRNA) technology offers highly specific gene silencing in diverse plant species. The principal challenge in amiRNA application is to select potent amiRNAs from hundreds of bioinformatically designed candidates to enable maximal target gene silencing at the protein level. To address this issue, we developed the epitope-tagged protein-based amiRNA (ETPamir) screens, in which single or multiple potential target genes encoding epitope-tagged proteins are constitutively or inducibly coexpressed with individual amiRNA candidates in plant protoplasts. Accumulation of tagged proteins, detected by immunoblotting with commercial tag antibodies, inversely and quantitatively reflects amiRNA efficacy in vivo. The core procedure, from protoplast isolation to identification of optimal amiRNA, can be completed in 2-3 d. The ETPamir screens circumvent the limited availability of plant antibodies and the complexity of plant amiRNA silencing at target mRNA and/or protein levels. The method can be extended to verify predicted target genes for endogenous plant miRNAs.

Signal transduction in maize and Arabidopsis mesophyll protoplasts

Plant protoplasts show physiological perceptions and responses to hormones, metabolites, environmental cues, and pathogen-derived elicitors, similar to cell-autonomous responses in intact tissues and plants. The development of defined protoplast transient expression systems for high-throughput screening and systematic characterization of gene functions has greatly contributed to elucidating plant signal transduction pathways, in combination with genetic, genomic, and transgenic approaches.

A cereal haemoglobin gene is expressed in seed and root tissues under anaerobic conditions

Legumes, and a very few non-legume plant species, are known to possess functioning haemoglobin genes. We describe here the characterization of a haemoglobin cDNA isolated from barley. The deduced amino acid sequence shows 71% amino acid identity with a non-legume haemoglobin gene, a further 16% of the residues being conservative replacements. The barley cDNA also hybridizes to genomic sequences in rye, maize and wheat. The demonstration of a gene from a monocotyledon with close sequence homology to the known non-legume plant haemoglobins fills a major gap in the known distribution of haemoglobin genes in the plant kingdom. The expression of the gene is induced in isolated barley aleurone layers exposed to anaerobic conditions, and the roots of flooding-stressed barley plants. The expression of the RNA under anoxic conditions is similar to that of a known anaerobic response gene, alcohol dehydrogenase. Our results suggest that the increased expression of haemoglobin RNA is an integral part of the normal anaerobic response in barley. The findings are discussed in the light of current theories of haemoglobin function and evolution.