Reduction of pyruvate orthophosphate dikinase activity is associated with high temperature-induced chalkiness in rice grains.
Global warming affects both rice (Oryza sativa) yields and grain quality. Rice chalkiness due to high temperature during grain filling would lower the grain quality. The biochemical and molecular mechanisms responsible for the increased occurrence of chalkiness under high temperature are not fully understood. Previous research suggested that cytosolic pyruvate orthophosphate dikinase (cyPPDK, EC 2.7.9.1) in rice modulates carbon metabolism. The objective of this study was to determine the relationship between cyPPDK and high temperature-induced chalkiness. High temperature treatments were applied during the grain filling of two rice cultivars (9311 and TXZ-25) which had different sensitivity of chalkiness to high temperature. Chalkiness was increased significantly under high temperature treatment, especially for TXZ-25. A shortened grain filling duration and a decreased grain weight in both cultivars were caused by high temperature treatment. A reduction in PPDK activities due to high temperature was observed during the middle and late grain filling periods, accompanied by down regulated cyPPDK mRNA and protein levels. The temperature effects on the developmental regulation of PPDK activity were confirmed at transcription, translation and post-translational levels. PPDK activities were insensitive to variation in PPDK levels, suggesting the rapid phosphorylation mechanism of this protein. The two varieties showed similar responses to the high temperature treatment in both PPDK activities and chalkiness. We concluded that high temperature-induced chalkiness was associated with the reduction of PPDK activity.
MOA Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Zhen-mei
ZM
Wang
MOA Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Hai-xia
HX
Li
MOA Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Xiong-feng
XF
Liu
MOA Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Ying
Y
He
MOA Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China. Electronic address: zenghl@mail.hzau.edu.cn.
Han-lai
HL
Zeng
D000222:Adaptation, Physiological; D015536:Down-Regulation; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D057232:Global Warming; D006358:Hot Temperature; D012275:Oryza / Q000201:enzymology / Q000378:metabolism* / Q000502:physiology; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011772:Pyruvate, Orthophosphate Dikinase / Q000235:genetics / Q000378:metabolism*; D011773:Pyruvates / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012639:Seeds / Q000378:metabolism*; D013045:Species Specificity; D013213:Starch / Q000378:metabolism
D010710:Phosphates; D010940:Plant Proteins; D011773:Pyruvates; D012333:RNA, Messenger; D013213:Starch; D011772:Pyruvate, Orthophosphate Dikinase
Chalkiness; High temperature; Pyruvate orthophosphate dikinase; Rice