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

DOMINGUEZ PG; FRANKEL N; IUSEM N; FERNIE AR; CARRARI F

Puerto Madryn, Argentina

Congreso; XLVI Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2010

Asr (ABA, stress, ripening) is a gene family widely distributed inhigher plants, whose products form group 7 of LEA proteins.Transcription of Asr genes is induced by different types of abioticstress and during fruit ripening. Grape and tomato ASR proteinshave been proposed to regulate the transcription of sugar- andabiotic stress-regulated genes in fruit and vegetative tissues,respectively. In this work, overexpressing and silenced Asr1tobacco plants were characterized. Silenced plants show shorterinternodes, loss of apical dominance, chlorosis, leaf necrosis andlate-flowering. Photosynthetic rates of these plants are diminishedunder a wide range of irradiances, while conductance andtranspiration are only diminished under saturation levels ofirradiance. Photosynthetic carbohydrate metabolism measurementsshowed that glucose levels of silenced plants are reduced during thediurnal cycle in comparison to wild-type plants. Phloem sap of overexpressingplants contains lower levels of sugars than that of wildtypeplants, 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. Inconclusion, all these observations support the proposed function ofASR proteins