Contrasting growth responses in lamina and petiole during neighbor detection depend on differential auxin responsiveness rather than different auxin levels

• Published in: The New phytologist 2015-10, Vol.208 (1), p.198-209
• Main Authors: Wit, Mieke, Ljung, Karin, Fankhauser, Christian
• Format: Article
• Language: English
• Subjects: Arabidopsis - growth & development; Arabidopsis - metabolism; Arabidopsis - physiology; Arabidopsis Proteins - metabolism; auxin; Auxins; Biosynthesis; Darkness; Detection; Developmental Biology; DNA-Binding Proteins - metabolism; Drug therapy; Elongation; Gene Expression; Gene expression regulation; Hormones; Hypocotyls; Indoleacetic Acids - metabolism; leaf growth; Leaves; Light; neighbor detection; Petioles; Pharmacology; PHYTOCHROME INTERACTING FACTOR (PIF); Plant cells; Plant growth; Plant Leaves - growth & development; Plant Leaves - metabolism; Plant Leaves - physiology; Plants; Receptors; Seedlings; Shade; shade avoidance response; Tissue; Tissues; Utvecklingsbiologi; XYLOGLUCAN ENDOTRANSGLUCOSYLASE/HYDROLASE (XTH)
• ISSN: 0028-646X; 1469-8137; 1469-8137
• DOI: 10.1111/nph.13449

Foliar shade triggers rapid growth of specific structures that facilitate access of the plant to direct sunlight. In leaves of many plant species, this growth response is complex because, although shade triggers the elongation of petioles, it reduces the growth of the lamina. How the same external cue leads to these contrasting growth responses in different parts of the leaf is not understood. Using mutant analysis, pharmacological treatment and gene expression analyses, we investigated the role of PHYTOCHROME INTERACTING FACTOR7 (PIF7) and the growthpromoting hormone auxin in these contrasting leaf growth responses. Both petiole elongation and lamina growth reduction are dependent on PIF7. The induction of auxin production is both necessary and sufficient to induce opposite growth responses in petioles vs lamina. However, these contrasting growth responses are not caused by different auxin concentrations in the two leaf parts. Our work suggests that a transient increase in auxin levels triggers tissue-specific growth responses in different leaf parts. We provide evidence suggesting that this may be caused by the different sensitivity to auxin in the petiole vs the blade and by tissue-specific gene expression.