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Physiology and Proteomics of Cabbage Under Heat and Flooding Stress

Chang KY, Lin KH, Lo YH and Lo HF

High temperature and excess rain, which can lead to heat and flooding stresses, seriously impact the yield and quality of cabbages. Two cabbage cultivars were examined in this study: heat- and flooding-tolerant ‘Sha-sha-jieu’ and heat-tolerant but flooding-sensitive ‘Mi-ni’. The goals of this study were to investigate leaf proteomic and physiological changes in plants responding to treatments of high temperature, flooding, and both stresses combined. Fortyfive- day-old cabbage plants at temperatures of 22°C or 40°C were treated separately with or without flooding in growth chambers for 0, 6, 12, 24, 48, and 72 h. Treatment at 22°C without flooding was used as the control. Changes in stomatal conductance and chlorophyll fluorescence of stressed leaves indicate that ‘Mi-ni’ suffered more severely than ‘Sha-sha-jieu’. Separated by 2-dimensional liquid phase fractionation, 25 and 26 expressed protein spots were extracted from the stressed leaves of ‘Mi-ni’ and ‘Sha-sha-jieu’, respectively. Most of the differentially expressed proteins identified by matrixassisted laser desorption/ ionization-time of flight mass spectrometry were involved in photosynthesis and ATP synthesis. The most highly expressed proteins were ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO), oxygen evolving enhancer (OEE), and chloroplastic ATP synthase. However, both serine/threonine protein phosphatase 7 inactive homolog and entatricopeptide repeat-containing protein At1g79540 exhibited relatively lower expression under high temperature and flooding. In response to high temperature and flooding, proteins such as RubisCO, OEE protein 1, and chloroplastic ATP synthase generally increased, indicating that the regulation of energy production is critical for tolerating heat and flood stressing in cabbages.