Sophisticated and high-throughput technologies for genetic manipulation are being devised all the time, and can provide rapid insight into gene function. But to realize the full potential of these methods, techniques for phenotyping need to keep pace. Boyes et al. report a scheme for phenotyping in Arabidopsis thaliana that is thorough, sensitive and high throughput, and that could provide a valuable framework for studying gene function in this plant.

The authors began by formulating a quantitative description of the development of wild-type Arabidopsis, covering its complete life cycle. This description has two aspects. First, they defined a series of developmental landmarks (and the times at which they occur), such as “emergence of the cotyledons”, “first flower open” and “flowering complete”. Second, they collected detailed morphological information as each developmental landmark was reached, such as “number of rosette leaves”, “sepal length” and “seed yield”. Overall, the authors described 14 developmental landmarks and 52 morphological traits. Importantly, these data can be collected efficiently and cheaply, and the authors also quantified the normal levels of variation for each measurement.

To test whether the collection of these phenotypic data can uncover developmental defects in Arabidopsis mutants, the authors looked at five mutants that had previously been described as having only minor or no morphological abnormalities. In each case, clear abnormalities were detected, which provide new information on the role of the corresponding genes in development. The function of FAE1 (FATTY ACID ELONGATION 1), for example, was thought to be confined to the seed, but striking defects in leaf production in the fae1-1 mutant imply that FAE1 is also required later in development.

This new scheme for phenotypic analysis provides a sensitive assay for identifying developmental defects in Arabidopsis mutants. If adopted more widely it could become a valuable standard, which will allow more robust comparison of the consequences of genetic, as well as environmental, perturbations to Arabidopsis development.