NaRALF, a peptide signal essential for the regulation of root hair tip apoplastic pH in Nicotiana attenuata, is required for root hair development and plant growth in native soils
Article first published online: 3 OCT 2007
The Plant Journal
Volume 52, Issue 5, pages 877–890, December 2007
How to Cite
Wu, J., Kurten, E. L., Monshausen, G., Hummel, G. M., Gilroy, S. and Baldwin, I. T. (2007), NaRALF, a peptide signal essential for the regulation of root hair tip apoplastic pH in Nicotiana attenuata, is required for root hair development and plant growth in native soils. The Plant Journal, 52: 877–890. doi: 10.1111/j.1365-313X.2007.03289.x
- Issue published online: 3 OCT 2007
- Article first published online: 3 OCT 2007
- Received 23 March 2007; revised 16 July 2007; accepted 2 August 2007.
- root hair;
- tip growth;
- extracellular pH oscillation;
- plant fitness;
- Nicotiana attenuata
Rapid alkalinization factor (RALF) is a 49-amino-acid peptide that rapidly alkalinizes cultivated tobacco cell cultures. In the native tobacco Nicotiana attenuata, NaRALF occurs as a single-copy gene and is highly expressed in roots and petioles. Silencing the NaRALF transcript by transforming N. attenuata with an inverted-repeat construct generated plants (irRALF) with normal wild-type (WT) above-ground parts, but with roots that grew longer and produced trichoblasts that developed into abnormal root hairs. Most trichoblasts produced a localized ‘bulge’ without commencing root hair tip growth; fewer trichoblasts grew, but were only 10% as long as those of WT plants. The root hair phenotype was associated with slowed apoplastic pH oscillations, increased pH at the tips of trichoblasts and decreased accumulation of reactive oxygen species in the root hair initiation zone. The root hair growth phenotype was partially restored when irRALF lines were grown in a low-pH-buffered medium, and reproduced in WT plants grown in a high-pH-buffered medium. When irRALF plants were grown in pH 5.6, 6.7 and 8.1 soils together with WT plants in glasshouse experiments, they were out-competed by WT plants in basic, but not acidic, soils. When WT and irRALF lines were planted into the basic soils of the native habitat of N. attenuata in the Great Basin Desert, irRALF plants had smaller leaves, shorter stalks, and produced fewer flowers and seed capsules than did WT plants. We conclude that NaRALF is required for regulating root hair extracellular pH, the transition from root hair initiation to tip growth and plant growth in basic soils.