Physiological and proteomic analyses of Korean F1 maize (Zea mays L.) hybrids under water-deficit stress during flowering

Despite the relevance of drought stress, the regulation of gene expression, protein accumulation, and plant physiology under water-deficit stress is not well understood in Korean F1 maize (Zea mays L.) hybrids. In this study, we investigated the effect of water deficit on the F1 maize hybrids, Ilmichal (Ilmi) and Gwangpyeongok (GPOK), by withholding water for 10 days during flowering. Water deficit severely reduced the relative water content, area, SPAD values, and stomatal conductance of leaves, stem length, and the dry matter content of aerial tissues in drought-stressed plants of both hybrids. However, the dry matter content of roots was reduced only in GPOK. Two-dimensional gel electrophoresis identified 24 spots representing proteins accumulated to differential levels in well-watered and drought-stressed plants of both hybrids. Further analysis of protein spots using matrix assisted laser desorption ionization–time of flight mass spectrometry and protein database searches revealed that nine proteins were involved in carbohydrate metabolism, seven in stress response, and two in photosynthesis. Among these proteins, delta 3,5-delta 2,4-dienoyl-CoA isomerase (spot 8) and bifunctional 3-phosphoadenosine 5-phosphosulfate synthetase 2 (spot 23) were present only in GPOK, whereas NAD-dependent epimerase/dehydratase (spot 13), NAD(P)H-quinone oxidoreductase subunit 2 A (spot 24), and an uncharacterized protein (spot 19) were present only in Ilmi, in response to water-deficit stress. Semi-quantitative reverse transcription PCR analysis showed that the transcript levels of most of the genes encoding these proteins correlated well with their protein levels, suggesting that water deficit affects gene transcription in F1 maize hybrids at the flowering stage.