Asr1 is involved in sugar signaling in tobacco plants

DOMINGUEZ PG; FRANKEL N; IUSEM ND; CARRARI F

San Luis

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Bioquímica y Biología Molecular (SAIB); 2011

SAIB

Asr (ABA, stress, ripening) genes belong to the group 7 of LEA proteins. Grape ASR1 protein has been proposed to regulate the transcription of the hexose transporter VvHt. Silenced Asr1 tobacco plants were characterized in detail at vegetative phase. Transgenic lines showed higher glucose levels in leaves, diminished CO2 assimilation, higher sugar contents in phloem sap, altered total protein pattern and foliar necrosis. This phenotype mimics tobacco leaf senescence. In agreement with this observation, the relative amount of ASR1 protein increases along with leaf age in wild-type plants. These results might indicate that ASR1 is involved in foliar senescence. Moreover, alterations in ABA and gibberellin levels and in sensitivity to GA3 were detected in the silenced lines, probably as a consequence of the interactions between sugar and hormone signalling. Expression analyses of a hexose transporter, NtHt, and a sucrose transporter-like, NtSut2, showed that their levels are reduced. These results suggest that Asr1 is involved in sugar signalling by a mechanism involving the regulation of sugar transporters gene expression and that the same mechanism contributes to modulate foliar senescence.