Drought is a major environmental factor that limits grain yield in rice. In order to understand
the proteomic changes in response to drought at reproductive stage, proteins expressed in the
young panicles were compared between two varieties of rice with contrasting tolernace to drought.
The identified 36 differentially expressed proteins are involved in energy production, metabolism,
stress defense, protein destination and cell structure. A coordinative up-regulation of triosephosphate
isomerase, glycin decarboxylase complex H-protein, glyoxylase I and cytosolic ascorbate peroxidase
was obseved in the drought tolerant variety Zhonghan 3, which may contribute to higher tolerance by
increasing the energy production and maintaining redox homeostasis. Two-dimensional Western
blotting experiments identified three APX1 and three APX2 isoforms up-regulated during drought
stress in drought-tolerant varieties (Zhonghan 3, IRAT109 and PRATAO). However, in droughtsuceptible
varieties (IR29, Zhengshan 97B and CATUNA), expression of the six isoforms was unchanged
or even down-regulated. Under normal growth conditions, expression level of the six APX
isoforms showed negative correlation with drought tolerance of rice. Our data suggested that APX
isoforms may be considered as indicators of the redox status that related to drought tolerance in rice.