Summary: Small non‐coding RNAs, including microRNAs (miRNAs) and small interfering RNAs (siRNAs), are effectors of regulatory pathways underlying plant development, metabolism, and responses to biotic and abiotic stresses. To address the nature and functions of these regulators in grapevine (Vitis vinifera L.), we have produced a small RNA library from mixed‐stage grape berries. Thirteen conserved miRNAs belonging to nine miRNA families, a non‐conserved miRNA, and four putative non‐conserved miRNAs were isolated, and their expression and targets are described. Experimentally validated targets of non‐conserved miRNAs and putative miRNAs included three genes encoding NB‐LRR proteins and a gene encoding a heavy metal ion transport/detoxification protein. Of the endogenous and pathogen‐derived siRNAs that were also isolated, four endogenous siRNAs mapped to genes encoding RD22‐like proteins and two to a gene encoding a cytokinin synthase. The siRNA id65 targeted the cytokinin synthase gene transcript with antisense complementarity, and was specifically expressed in mature berries, in which, by contrast, expression of the cytokinin synthase gene was strongly repressed. 5′ RACE revealed that the transcript of this gene was processed in 21 nucleotide increments from the id65 cleavage site, and that further cleavage was mediated by secondary siRNAs in cis. These results indicate that grapevine miRNA‐ and siRNA‐mediated regulatory circuits have evolved to comprise processes associated with defence and fruit ripening, and broaden the range of small RNA‐mediated regulation, which was previously associated with auxin, ABA, gibberellins and jasmonate, to encompass cytokinin metabolism.

Poplar (Populus spp.) is a high-value crop for wood and biomass production and a model organism for tree physiology and genomics. The early release, in 2006, of the complete genome sequence of P. trichocarpa was followed by a wealth of studies that significantly enriched our knowledge of complex pathways inherent to woody plants, such as lignin biosynthesis and secondary cell wall deposition. Recently, in the attempt to cope with the challenges posed by ongoing climate change, fundamental studies and breeding programs with poplar have gradually shifted their focus to address the responses to abiotic stresses, particularly drought. Taking advantage from a set of modern genomic and phenotyping tools, these studies are now shedding light on important processes, including embolism formation (the entry and expansion of air bubbles in the xylem) and repair, the impact of drought stress on biomass yield and quality, and the long-term effects of drought events. In this review, we summarize the status of the research on the molecular bases of the responses to drought in poplar. We highlight how this knowledge can be exploited to select more tolerant genotypes and how it can be translated to other tree species to improve our understanding of forest dynamics under rapidly changing environmental conditions.