Rop1Ps promote actin cytoskeleton dynamics and control the tip growth of lily pollen tube
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Rop, the small GTPase of the Rho family in plants, is believed to exert molecular control over dynamic changes in the actin cytoskeleton that affect pollen tube elongation characteristics. In the present study, microinjection of Rop1Ps was used to investigate its effects on tip growth and evidence of interaction with the actin cytoskeleton in lily pollen tubes. Microinjected wild type WT-Rop1Ps accelerated pollen tube elongation and induced actin bundles to form in the very tip region. In contrast, microinjected dominant negative DN-rop1Ps had no apparent effect on pollen tube growth or microfilament organization, whereas microinjection of constitutively active CA-rop1Ps induced depolarized growth and abnormal pollen tubes in which long actin bundles in the shank of the tube were distorted. Injection of phalloidin, a potent F-actin stabilizer that inhibits dynamic changes in the actin cytoskeleton, prevented abnormal growth of the tubes and suppressed formation of distorted actin bundles. These results indicate that Rop1Ps exert control over important aspects of tip morphology involving dynamics of the actin cytoskeleton that affect pollen tube elongation.
KeywordsSmall GTPase Rop Microinjection Pollen tube growth Actin cytoskeleton
We thank Prof. Dr. Zhenbiao Yang (University of California, Riverside, USA) for kindly providing all constructs and for his comments on the manuscript. We thank Dr. Ming Yuan (China Agricultural University) for critical reading and comments on the manuscript. This work was supported by the National Natural Science Foundation for Distinguished Young Scholars (Grant No. 30325005), the National Natural Science Foundation of China (Grant No. 30270087), the National Basic Research Program of China (Grant No. 2006CB100100) and the Key Laboratory Research Foundation of State Education Ministry of China for Visiting Scholars.
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