Nitrogen stress response of a hybrid species: a gene expression study

Low soil fertility limits growth and productivity in many natural and agricultural systems, where the ability to sense and respond to nutrient limitation is important for success. Helianthus anomalus is an annual sunflower of hybrid origin that is adapted to desert sand-dune substrates with lower fertility than its parental species, H. annuus and H. petiolaris. Previous studies have shown that H. anomalus has traits generally associated with adaptation to low-fertility habitats, including a lower inherent relative growth rate and longer leaf lifetime.

Here, a cDNA microarray is used to identify gene expression differences that potentially contribute to increased tolerance of low fertility of the hybrid species by comparing the nitrogen stress response of all three species with high- and low-nutrient treatments.

Relative to the set of genes on the microarray, the genes showing differential expression in the hybrid species compared with its parents are enriched in stress-response genes, developmental genes, and genes involved in responses to biotic or abiotic stimuli. After a correction for multiple comparisons, five unique genes show a significantly different response to nitrogen limitation in H. anomalus compared with H. petiolaris and H. annuus. The Arabidopsis thaliana homologue of one of the five genes, catalase 1, has been shown to affect the timing of leaf senescence, and thus leaf lifespan.

The five genes identified in this analysis will be examined further as candidate genes for the adaptive stress response in H. anomalus. Genes that improve growth and productivity under nutrient stress could be used to improve crops for lower soil fertility which is common in marginal agricultural settings.