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Polyploidy is a common event in plants that involves the acquisition of more than two complete sets of chromosomes. Allopolyploidy originates from interspecies hybrids while autopolyploidy originates from intraspecies whole genome duplication (WGD) events. In spite of inconveniences derived from chromosomic rearrangement during polyploidization, natural plant polyploids species often exhibit improved growth vigour and adaptation to adverse environments, conferring evolutionary advantages. These advantages have also been incorporated into crop breeding programmes. Many tetraploid crops show increased stress tolerance, although the molecular mechanisms underlying these different adaptation abilities are poorly known. Understanding the physiological, cellular, and molecular mechanisms coupled to WGD, in both allo- and autopolyploidy, is a major challenge. Over the last few years, several studies, many of them in Arabidopsis, are shedding light on the basis of genetic, genomic, and epigenomic changes linked to WGD. In this review we summarize and discuss the latest advances made in Arabidopsis polyploidy, but also in other agronomic plant species. © 2015 The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved.

10 p.-5 fig.-1 tab. Alberto Coego et alt., Transcription factors (TFs) are key regulators of gene expression in all organisms. In eukaryotes, TFs are often represented by functionally redundant members of large gene families. Overexpression might prove a means to unveil the biological functions of redundant TFs; however, constitutive overexpression of TFs frequently causes severe developmental defects, preventing their functional characterization. Conditional overexpression strategies help to overcome this problem. Here, we report on the TRANSPLANTA collection of Arabidopsis lines, each expressing one of 949 TFs under the control of a β–estradiol-inducible promoter. Thus far, 1636 independent homozygous lines, representing an average of 2.6 lines for every TF, have been produced for the inducible expression of 634 TFs. Along with a GUS-GFP reporter, randomly selected TRANSPLANTA lines were tested and confirmed for conditional transgene expression upon β–estradiol treatment. As a proof of concept for the exploitation of this resource, β–estradiol-induced proliferation of root hairs, dark-induced senescence, anthocyanin accumulation and dwarfism were observed in lines conditionally expressing full-length cDNAs encoding RHD6, WRKY22, MYB123/TT2 and MYB26, respectively, in agreement with previously reported phenotypes conferred by these TFs. Further screening performed with other TRANSPLANTA lines allowed the identification of TFs involved in different plant biological processes, illustrating that the collection is a powerful resource for the functional characterization of TFs. For instance, ANAC058 and a TINY/AP2 TF were identified as modulators of ABA-mediated germination potential, and RAP2.10/DEAR4 was identified as a regulator of cell death in the hypocotyl–root transition zone. Seeds of TRANSPLANTA lines have been deposited at the Nottingham Arabidopsis Stock Centre for further distribution., This research was supported by the CONSOLIDER TRANSPLANTA CSD2007-00057 grant from the Ministerio de Ciencia e Innovaci on (MICINN), and by BIO2011-27526 and BIO2010-15589 grants from the Ministerio de Econom ıa y Competitividad (to J.L. and J.A.J., respectively).

Plants are sessile organisms that have to adapt their growth to the surrounding environment. Concomitant with this adaptation capability, they have adopted a post-embryonic development characterized by continuous growth and differentiation abilities. Constant growth is based on the potential of stem cells to divide almost incessantly and on a precise balance between cell division and cell differentiation. This balance is influenced by environmental conditions and by the genetic information of the cell. Among the internal cues, the cross-talk between different hormonal signalling pathways is essential to control this division/differentiation equilibrium. Auxin, one of the most important plant hormones, regulates cell division and differentiation, among many other processes. Amazing advances in auxin signal transduction at the molecular level have been reported, but how this signalling is connected to the cell cycle is, so far, not well known. Auxin signalling involves the auxin-dependent degradation of transcription repressors by F-box-containing E3 ligases of ubiquitin. Recently, SKP2A, another F-box protein, was shown to bind auxin and to target cell-cycle repressors for proteolysis, representing a novel mechanism that links auxin to cell division. In this review, a general vision of what is already known and the most recent advances on how auxin signalling connects to cell division and the role of the ubiquitin pathway in plant cell cycle will be covered. © The Author 2013.