Transient VENUS

This year’s transit of Venus reminds me – albeit belatedly – to applaud the hard-working botanists of the Universities of Nottingham (UK), Ghent (Belgium), Leeds (UK) and Lyon (France) who have been exploring a more down-to-Earth – and ultimately more useful? – kind of Venus. Like all good phytologists they are interested in understanding the role of auxin in plant development. In order to get a better understanding of auxin biology it is important to identify where it actually works inside plant cells; a tall order, locating a tiny molecule in a small cell. Hitherto, a so-called DR5-based protocol was employed to monitor auxin distribution in planta. However, this reporter activity does not directly relate to endogenous auxin abundance. Recognising this limitation, Géraldine Brunoud et al. have developed ‘A novel sensor to map auxin response and distribution at high spatio-temporal resolution’. The group have engineered a new synthetic auxin signalling sensor in the model plant Arabidopsis thaliana using VENUS (a fast-maturing form of yellow fluorescent protein) fused to the Aux/IAA auxin-interaction domain (termed domain II; DII), hence its name DII-VENUS. Amongst DII-VENUS’ attributes are that its abundance is dependent on auxin, and it provides a map of relative auxin distribution at cellular resolution in different tissues. As proof of its usefulness, its rapid degradation in response to auxin has been exploited to visualise dynamic changes in cellular auxin distribution during two developmental responses, root gravitropism and lateral organ production at the shoot apex. A most pleasing symmetry, celestial transience mirrored in a more terrestrial context. Fiat lux!