Aluminium-responsive genes in sugarcane: identification and analysis of expression under oxidative stress

Suppression subtractive hybridization (SSH) technology was used to gain preliminary insights into gene expression induced by the phytotoxic aluminium species, Al(3+), in sugarcane roots. Roots of hydroponically-grown Saccharum spp. hybrid cv. N19 were exposed to 221 microM Al(3+) at pH 4.1 for 24 h, a regime shown to inhibit root elongation by 43%, relative to unchallenged roots. Database comparisons revealed that, of a subset of 50 cDNAs ostensibly up-regulated by the metal in the root tips, 14 possessed putative identities indicative of involvement in signalling events and the regulation of gene expression, while the majority (28) were of unknown function. All of the 50 cDNAs sequenced displayed significant similarity to uncharacterized plant expressed sequence tags (ESTs), approximately half (23) of which had been derived from other graminaceous crop species that had been subject to a variety of stresses. Analysis of the expression of 288 putative Al(3+)-inducible genic fragments indicated higher levels of expression under oxidative (1 mM diamide for 4 h) rather than Al(3+) stress. By deploying SSH, this study has provided an indication of the nature of genes expressed in sugarcane roots under Al(3+) stress. It is anticipated that the information obtained will guide further exploration of the potential for manipulation of the Al tolerance characteristics of the crop.