Nutrient use efficiency

Nutrient use efficiency

Nutrient use efficiency (NUE) may be defined as yield per unit input. In agriculture this is usually related to the input of fertiliser, whereas in scientific literature the NUE is often expressed as fresh weight or product yield per content of nutrient. Improvement of NUE is an essential pre-requisite for expansion of crop production into marginal lands with low nutrient availability. The nutrients most commonly limiting plant growth are N, P, K and S. NUE depends on the ability to efficiently take up the nutrient from the soil, but also on transport, storage, mobilization, usage within the plant, and even on the environment. Two major approaches may be taken to understand NUE. Firstly, the response of plants to nutrient deficiency stress can be explored to identify processes affected by such stress and those that may serve to sustain growth at low nutrient input. A second approach makes use of natural or induced genetic variation. NUE can be advantageously analyzed through quantitative trait locus (QTL) analysis in recombinant inbred or near isogenic lines (RIL, NIL) sets derived from crosses between wild accessions, which show tremendous variation for most physiological traits studied. For this, Arabidopsis is an ideal model plant as many different RILs exist with different parental ecotypes, which when in combination with the availability of genomic sequence enables the use of quantitative genetics to identify the genetic factors responsible for such variation. Alternatively, Arabidopsis mutant populations can be screened for mutants less sensitive to growth inhibition by low nutrient conditions. The information obtained from Arabidopsis can be translated into crops by identifying target genes for breeding.

Natural variation
In the first attempt to investigate the genetic variation in nutrient use efficiency we compared growth of 10 Arabidopsis ecotypes on normal and limiting concentrations of N (1 mM) and P (0.1 mM). A great variation in the degree of growth reduction was observed between the ecotypes. Evidently, some ecotypes (Ga-0, Col-0, Kil) are better adapted to growth at N-limiting conditions whereas others (Kil, Sha) are better coping with P deficiency. We are using a variety of analyses to identify processes responsible for the better adaptation to growth at limiting N conditions.

Relevant publication
North K.A., Ehlting B., Koprivova A., Rennenberg H., Kopriva S. (2009) Natural variation in Arabidopsis adaptation to growth at low nitrogen conditions. Plant Physiol. Biochem., 47, 912-918

Forward genetic screen
We made a small scale screen with Arabidopsis activation lines to identify mutants growing better at low input of nitrate, sulfate, and phosphate than wild type. In the verified mutants the genes underlying the phenotypes will be cloned by expression analysis of genes adjacent to sites of T-DNA insertions that are identified by TAIL-PCR.