Title

Response to zinc deficiency of two rice lines with contrasting tolerance is determined by root growth maintenance and organic acid exudation rates, and not by zinc-transporter activity

Document Type

Article

Publication details

Widod, Broadley, MR, Rose, TJ, Frei, M, Pariasca-Tanaka, J, Yoshihashi, T, Thomson, M, Hammond, JP, Aprile, A, Close, TJ, Ismail, AM & Wissuwa, M 2010, 'Response to zinc deficiency of two rice lines with contrasting tolerance is determined by root growth maintenance and organic acid exudation rates, and not by zinc-transporter activity', New Phytologist, vol. 186, no. 2, pp. 400-414.

Published version available from:

http://dx.doi.org/10.1111/j.1469-8137.2009.03177.x

Peer Reviewed

Peer-Reviewed

Abstract

• Zinc (Zn)-deficient soils constrain rice (Oryza sativa) production and cause Zn malnutrition. The identification of Zn-deficiency-tolerant rice lines indicates that breeding might overcome these constraints. Here, we seek to identify processes underlying Zn-deficiency tolerance in rice at the physiological and transcriptional levels.

• A Zn-deficiency-tolerant line RIL46 acquires Zn more efficiently and produces more biomass than its nontolerant maternal line (IR74) at low [Zn]ext under field conditions. We tested if this was the result of increased expression of Zn2+ transporters; increased root exudation of deoxymugineic acid (DMA) or low-molecularweight organic acids (LMWOAs); and⁄or increased root production. Experiments were performed in field and controlled environment conditions.

• There was little genotypic variation in transcript abundance of Zn-responsive root Zn2+-transporters between the RIL46 and IR74. However, root exudation of DMA and LMWOA was greater in RIL46, coinciding with increased root expression of putative ligand-efflux genes. Adventitious root production was maintained in RIL46 at low [Zn]ext, correlating with altered expression of root-specific auxinresponsive genes.

• Zinc-deficiency tolerance in RIL46 is most likely the result of maintenance of root growth, increased efflux of Zn ligands, and increased uptake of Zn-ligand complexes at low [Zn]ext; these traits are potential breeding targets.