基金We are grateful to Dr. Klaas van Wijk （Cornell University） for his critical comments and helpful suggestions to improve this paper. We thank Dr. Hongbtn Zhang for performing the BiFC experiments between CIpS1 and TAC/CIpF, Ms. Caroline Rodriguez, Sarah Melesse （Cornell University）, and Carmen Schubert （University of Freiburg） for technical assistance. We thank Dr. Julian Koschmleder （University of Freiburg） for supplying antibodies against PDS and ZDS, Dr. Philippe Hugueney （Universite de Strasbourg, France） for anti-DXS antibodies, and Dr. Roberto Bassi （Univerait＆ di Verona, Italy） for antibodies against LUT5. This work was supported by Agriculture and Food Research Initiative competitive award no. 2016-67013-24612 from the USDA National Institute of Food and Agriculture and by the HarvestPlus research consortium （2014H6320.FRE）. The authors declare no conflict of interest.