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The expression of gluten proteins measured by SE-HPLC and different mass spectrometer analyses following abiotic stress treatments
M. T. LABUSCHAGNE (1), A. van Biljon (1). (1) University of the Free State, Bloemfontein, South Africa

The impact of drought, cold and heat stress on gluten proteins was studied on two irrigation (Kariega and Duzi) and two dryland spring (PAN 3471 and PAN3478) bread wheat cultivars. The plants (three replications, 15 pots per replication, three plants per pot) were grown under greenhouse conditions. Treatments (heat, cold and drought stress and a control) were initiated when the kernels on the main tiller were at soft dough stage. The main tiller in each pot at the time of treatment was marked for later gluten analysis. Cold treatment was performed by placing the plants in climate cabinets in the following cycle (5°C, 30 minutes; 1°C less every 30 minutes until it reached -5.5°C, left 3 hours; -2°C, 30 minutes, 0°C, 30 minutes; 2°C, 30 minutes; 5°C, 30 minutes; back to green-house). For the heat treatment, plants were placed in climate cabinets at 32°C/15°C day/night treatment for 72 hours and then taken back to the green-house. Drought stress was applied by withholding watering until severe wilting was visible and then watering resumed as normal. A control set of plants was left in the greenhouse. Size exclusion HPLC and quality analyses were done on three replications of each entry for each treatment. All four treatments with three replications of PAN2378 was further analysed with the Orbitrap mass spectrometer and with MALDI-TOF mass spectrometry. The four cultivars showed different reactions to the different stress treatments, and some of the cultivars were more sensitive to stress, indicating that tolerance levels were genetically influenced. There was a strong relationship between the polymeric proteins (both SDS soluble and insoluble) and baking quality characteristics in all the cultivars for all treatments. The Orbitrap analysis showed that stress treatments altered the expression of the high molecular weight gluten proteins.

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