ci21A/Asr1 expression influences glucose accumulation in potato tubers

Abstract

Asr genes are exclusively found in thegenomes of higher plants. In many species, this genefamily is expressed under abiotic stress conditions andduring fruit ripening. The encoded proteins havenuclear localisation and consequently a transcriptionfactor function has been suggested. Interestingly, yeastone-hybrid experiments revealed that a grape ASRbinds to the promoter of a hexose transporter gene(VvHT1). However, the role of these proteins in plantais still elusive. By using a reverse genetics approach inpotato we found that modification of Asr1 expressionhas no incidence on the aerial phenotype of the plantbut exerts a dramatic effect in tuber. Asr1 antisensepotatoes displayed decreased tuber fresh weightwhereas Asr1 overexpressors had a diminished numberof tubers. Moreover, overexpression lines showed lowertranscript levels of a plasma membrane hexose transporterand a concomitant decrease in glucose content inparenchyma cells of potato tubers. On the same handglucose uptake rate was also reduced in one of theoverexpressing lines. It thus seems likely that Asr1 isinvolved in the control of hexose uptake in heterotrophicorgans. In addition, the transgenic plants werecharacterized by several other changes in steady statemetabolite levels. Results presented here support a rolefor ci21A/Asr1 in glucose metabolism of potato tuber.