Department of Plant Sciences

Phosphorus deficiency results in the formation of longer root hairs in Brassica carinata cv. Bale to exhaust a greater soil volume. Recently, suppression subtractive hybridization revealed genes that were regulated in P-starved roots in Brassica carinata. Sequencing identified genes sharing homologies to a leucine-rich repeat protein kinase (LRR), a transcription factor of the 14-3-3 family, and a proline rich family protein (PRP) in Arabidopsis thaliana. This study aims at characterizing the expression pattern of these putative P-responsive genes by specifying the response to several nutritional stress factors and by inducing or discontinuing phosphorus deprivation. Root hair length was enhanced with phosphorus and nitrogen deprivation but not with potassium depletion. Likewise, the transcription level of LRR and PRP was increased in -P and -N conditions whereas there was no clear response for 14-3-3. One day after varying P supply, phenotypically the root hair length was changed. Correspondingly, the expression of the root-specific LRR and PRP was induced by P-deficiency and inhibited by the addition of P. The response to P starvation of 14-3-3 followed no clear trend. P-resupply increased the gene expression as well as P removal with a short term repression after 3 hours. In summary, the expression of a LRR receptor-like protein kinase and a proline rich protein suggests a function of these genes in inducing root hair growth. The putative transcription factor 14-3-3 may be of importance in rapid but unspecific stress response.