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Contribution of NAC Transcription Factors to Plant Adaptation to Land

Science  28 Mar 2014:
Vol. 343, Issue 6178, pp. 1505-1508
DOI: 10.1126/science.1248417

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From Drips to Tubes

In the evolutionary transition from aquatic to terrestrial habitats, plants acquired internal systems to transport water and provide structural support. Xu et al. (p. 1505, published online 20 March) studied a family of genes and the cells they control to better understand the innovations required to adapt to dry land. In Arabidopsis, specific transcription factors regulate development of xylem—the plant tissue that transports water. The moss Physcomitrella patens has similar genes, which regulate development of hydroids and stereids, cells specialized in water transport and structural support. The similarity in the genes and their functions suggests the evolutionary origins of land-plant vascular systems.

Abstract

The development of cells specialized for water conduction or support is a striking innovation of plants that has enabled them to colonize land. The NAC transcription factors regulate the differentiation of these cells in vascular plants. However, the path by which plants with these cells have evolved from their nonvascular ancestors is unclear. We investigated genes of the moss Physcomitrella patens that encode NAC proteins. Loss-of-function mutants formed abnormal water-conducting and supporting cells, as well as malformed sporophyte cells, and overexpression induced ectopic differentiation of water-conducting–like cells. Our results show conservation of transcriptional regulation and cellular function between moss and Arabidopsis thaliana water-conducting cells. The conserved genetic basis suggests roles for NAC proteins in the adaptation of plants to land.

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