Plant biology

Auxin signals see the light

Science's STKE  26 Mar 2002:
Vol. 2002, Issue 125, pp. tw117
DOI: 10.1126/stke.2002.125.tw117

Tian et al. studied the mechanism by which the auxin and indole-3 acetic acid (Aux/IAA) genes regulate auxin responsiveness. They focused on the SHY2 member of this family and analyzed a loss-of-function and a gain-of-function mutant. Transcription analysis of Arabidopsis provides molecular support for the Aux/IAA protein SHY2 as a repressor of auxin-stimulated gene expression, including its own expression. Furthermore, a connection between metabolism, light, and auxin was found. SHY2 expression was induced by light in the absence of sucrose, but was decreased by light in the presence of sucrose. Imaizumi et al. studied light regulation of development in the moss Physomitrella patens. They identified the blue light receptor genes and used homologous recombination to create plants lacking the two cryptochromes (blue-light receptors) separately or in combination. The disruptant plants exhibited altered growth in blue light and demonstrated hyperresponsiveness to exogenous auxin. Several experiments suggested that cryptochromes signaling normally represses auxin signaling and that this repression is lost in the cry mutants. Together these two papers provide genetic evidence that light and auxin signaling pathways intersect and one point of intersection may be the auxin response repressors of the Aux/IAA family.

Q. Tian, N. J. Uhlir, J. W. Reed, Arabidopsis SHY2/IAA3 inhibits auxin-regulated gene expression. Plant Cell 14, 301-319 (2002). [Online Journal]

T. Imaizumi, A. Kadota, M. Hasebe, M. Wada, Cryptochrome light signals control development to suppress auxin sensitivity in the moss Physcomitrella patens. Plant Cell 14, 373-386 (2002). [Online Journal]