The microalga Haematococcus pluvialis accumulates astaxanthin in response to abiotic stresses. Since methyl jasmonate (MJ) and gibberellins A(3) (GA(3)) are involved in the stress responses of plants, the impact of these compounds on astaxanthin metabolism was studied. Alga cells treated separately with MJ and GA(3) accumulated more astaxanthin than the controls. MJ and GA(3) treatment increased the transcription of three beta-carotene ketolase genes (bkts). MJ- and GA(3)-responsive cis-acting elements were identified in the 5'-flanking regions of bkt genes. These results suggest that MJ and GA(3) constitute molecular signals in the network of astaxanthin accumulation. Induction of astaxanthin accumulation by MJ or GA(3) without any other stimuli presents an attractive application potential. (C) 2010 Elsevier Ltd. All rights reserved.