Identification of genes induced in proteoid roots of white lupin under nitrogen and phosphorus deprivation, with functional characterization of a formamidase

Abstract

White lupin (Lupinus albus L.) is considered a model system for understanding plant acclimation to nutrient deficiency. It acclimates to phosphorus (P) and iron (Fe) deficiency by the development of short, densely clustered lateral roots called proteoid (or cluster) roots; proteoid-root development is further influenced by nitrogen (N) supply. In an effort to better understand proteoid root function under various nutrient deficiencies, we used nylon filter arrays to analyze 2,102 expressed sequence tags (ESTs) from proteoid roots of P-deficient white lupin. These have been previously analyzed for up-regulation in −P proteoid roots, and were here analyzed for upregulation in proteoid roots of N-deprived plants. We identified a total of 19 genes that displayed upregulation in proteoid roots under both P and N Plant Soil (2010) 334:137-150 deprivation. One of these genes showed homology to putative formamidases. The corresponding open reading frame was cloned, overexpressed in E. coli, and the encoded protein was purified; functional characterization of the recombinant protein confirmed formamidase activity. Though many homologues of bacterial and fungal formamidases have been identified in plants, to our knowledge, this is the first report of a functional characterization of a plant formamidase.

Improving phosphorus use efficiency in agriculture: opportunities for breeding

“…These are also most prominent in the upper soil layer and are thought to be mainly effective by mobilising P through exudation of organic acids rather than by scavenging through root extension (Rath et al 2010, see also section on physiology below). Lupins combine this trait with an absence of mycorrhiza (with arbuscular mycorrhizal fungi (AMF), see further in section on mycorrhiza below).…”

“…These exudates appear to be most effectively targeted to mobilizable P in the soil by the proteoid (cluster) roots in some lupin species (Rath et al 2010). The exudates include protons and organic acids, such as citrate, malate, and oxalate.…”

Root Architecture Responses: In Search of Phosphate

“…Their formation is an adaptive mechanism of specialist, mostly nonmycorrhizal plant species that thrive in environments with scarce nutrient availability (Shane and Lambers, 2005). Their development has, so far, largely been investigated under phosphorus-limited conditions, but it is also affected by nitrogen and iron availability (Arahou and Diem, 1997;Zaid et al, 2003;McCluskey et al, 2004;Rath et al, 2010). CR structure and physiology are geared to enlarge the surface area of the root for the exudation of large amounts of carboxylates (exudative burst) to generate high local concentrations for the mining of insoluble forms of Pi from the soil and the efficient uptake of Pi (Neumann and Martinoia, 2002;Lambers et al, 2006).…”

An RNA-Seq Transcriptome Analysis of Orthophosphate-Deficient White Lupin Reveals Novel Insights into Phosphorus Acclimation in Plants

“…Previously, we reported enhanced expression of formamidase and formate dehydrogenase in PdCR . Recently, Rath et al (2010) expressed a recombinant form of white lupin P i deficiency-induced formamidase and demonstrated activity with formamide. However, formamide is an unusual compound to be found in plants, and the K m of formamidase for formamide is high, suggesting that it may act on other substrates.…”