ASR PROTEINS ARE INVOLVED IN THE ABA-GA CROSS-TALK ALTERING PHOTOSYNTHETIC METABOLISM

DOMINGUEZ, P.G.; FRANKEL, NICOLÁS; IUSEM, NORBERTO D; CARRARI, FERNANDO

Congreso; XLVI Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2010

Asr (ABA, stress, ripening) is a gene family widely distributed in higher plants, whose products form group 7 of LEA proteins. Transcription of Asr genes is induced by different types of abiotic stress and during fruit ripening. Grape and tomato ASR proteins have been proposed to regulate the transcription of sugar- and abiotic stress-regulated genes in fruit and vegetative tissues, respectively. In this work, overexpressing and silenced Asr1 tobacco plants were characterized. Silenced plants show shorter internodes, loss of apical dominance, chlorosis, leaf necrosis and late-flowering. Photosynthetic rates of these plants are diminished under a wide range of irradiances, while conductance and transpiration are only diminished under saturation levels of irradiance. Photosynthetic carbohydrate metabolism measurements showed that glucose levels of silenced plants are reduced during the diurnal cycle in comparison to wild-type plants. Phloem sap of over-expressing plants contains lower levels of sugars than that of wild-type plants, while the opposite was observed in silenced plants. ABA levels in expanded leaves from silenced plants are reduced, though they preserve the sensitivity to exogenous GA3. In conclusion, all these observations support the proposed function of ASR proteins.