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ARS Home » Northeast Area » Washington, D.C. » National Arboretum » Floral and Nursery Plants Research » Research » Publications at this Location » Publication #404697

Research Project: Evaluation and Genetic Improvement of Woody Ornamental Landscape Plants

Location: Floral and Nursery Plants Research

Title: Root predominant overexpression of iaaM and CKX genes promotes root initiation and biomass production and initiation in citrus

item TANG, DAN - University Of Connecticut
item LI, YANJUN - University Of Connecticut
item ZHAI, LONGMEI - University Of Connecticut
item WANG, XIAOJING - University Of Connecticut
item LI, WEI - University Of Connecticut
item KUMAR, RAHUL - University Of Connecticut
item YER, HUSEVIN - University Of Connecticut
item Duan, Hui
item CHENG, BAOPING - Guangdong Academy Of Agricultural Sciences
item DENG, ZINIU - Hunan Agricultural University
item LI, YI - University Of Connecticut

Submitted to: Plant Cell Tissue and Organ Culture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2023
Publication Date: 7/20/2023
Citation: Tang, D., Li, Y., Zhai, L., Wang, X., Li, W., Kumar, R., Yer, H., Duan, H., Cheng, B., Deng, Z., Li, Y. 2023. Root predominant overexpression of iaaM and CKX genes promotes root initiation and biomass production and initiation in citrus. Plant Cell Tissue and Organ Culture.

Interpretive Summary: Root systems in plants provide stability and support and absorb nutrients and water for plant growth and development. Plant roots can also be used as bioreactors for producing plant-specific bioactive molecules. Therefore, induction and development of a robust root system is critical for many plant-based industries including propagation of woody plants. Changing the ratios of the plant growth regulators auxin and cytokinin affects root development in plants; however, little research has been done to genetically manipulate auxin and cytokinin levels in woody plants, particularly in a root specific manner. Using citrus as a model, a team of scientists developed a technology that overexpresses an auxin biosynthesis gene (increases auxin production) or overexpresses a cytokinin catabolism gene (decreases cytokinin levels) in root tissue. The resulting transgenic plants have enhanced rooting capacity from shoot explants and enhanced root biomass production. This technology greatly enhances root initiation and growth of citrus plants and is also applicable to other woody plants.

Technical Abstract: Promoting initiation and biomass production of roots is significant for plant-based industries including using roots as bioreactors. We used two citrus genotypes, Carrizo and US-897, as model plants to test the effects of root-predominantly overexpressed the iaaM (indoleacetic acid-tryptophan monooxygenase) gene and a CKX (a cytokinin oxidase/dehydrogenase) gene. The iaaM transgenic lines exhibited markedly faster root initiation, more root numbers, and higher root biomass compared to their wild-type counterparts. The transgenic iaaM + CKX plants also exhibited similar phenotypes, albeit to a lesser extent than the iaaM plants. Molecular analysis revealed an auxin-responsive CsGH3.1 gene was up-regulated in the iaaM roots and iaaM + CKX roots, and a cytokinin-responsive gene CsARR5 gene was down-regulated in the iaaM + CKX roots. Our results demonstrate that root predominant overexpression of the iaaM or both the iaaM and CKX genes drastically enhances the initiation, growth and biomass production of roots. These results provide additional support that manipulation of auxin and cytokinin levels in roots via transgenic or gene-editing technologies may benefit production of high-value secondary metabolites using roots as bioreactors and also improve rooting of recalcitrant plant species.