Strategies for improving plant size are critical targets for plant biotechnology to increase vegetative biomass or reproductive yield. To improve biomass production, a codon-optimized helix–loop–helix transcription factor (VvCEB1opt) from wine grape was overexpressed in Arabidopsis thaliana resulting in significantly increased leaf number, leaf and rosette area, fresh weight and dry weight. Cell size, but typically not cell number, was increased in all tissues resulting in increased vegetative biomass and reproductive organ size, number and seed yield. Ionomic analysis of leaves revealed the VvCEB1opt-overexpressing plants had significantly elevated, K, S and Mo contents relative to control lines. Increased K content likely drives increased osmotic potential within cells leading to greater cellular growth and expansion. To understand the mechanistic basis of VvCEB1opt action, one transgenic line was genotyped using RNA-Seq mRNA expression profiling and revealed a novel transcriptional reprogramming network with significant changes in mRNA abundance for genes with functions in delayed flowering, pathogen–defence responses, iron homeostasis, vesicle-mediated cell wall formation and auxin-mediated signalling and responses. Direct testing of VvCEB1opt-overexpressing plants showed that they had significantly elevated auxin content and a significantly increased number of lateral leaf primordia within meristems relative to controls, confirming that cell expansion and organ number proliferation were likely an auxin-mediated process. VvCEB1opt overexpression in Nicotiana sylvestris also showed larger cells, organ size and biomass demonstrating the potential applicability of this innovative strategy for improving plant biomass and reproductive yield in crops.
Bibliographical noteFunding Information:
This work was supported by the Department of Energy, Office of Science, Genomic Science Program under award number DESC0008834 and the National Institute of General Medical Sciences of the National Institutes of Health under INBRE Grant Number P20 RR016464 and COBRE Grant Number P20 GM103554. S.D.L. acknowledges the support from the National Research Foundation of Korea—Postdoctoral Fellowship Abroad Program NRF-2014R1A6A3A03055754. The authors would like to thank Pat Kysar (U.C. Davis Electron Microscopy Lab) for scanning electron microscopy, Jayanti Suresh for auxin analyses and the Research Analytical Laboratory at the University of Minnesota for ionomic analyses. Special thanks to Dr. Pradeep Yerramsetty, Pume Praphatanant, Melody Hsu and Sojeong Lee for providing technical assistance and Mary Ann Cushman and Lisa Petrusa for providing clarifying comments on the manuscript.
© 2018 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.
- Arabidopsis thaliana
- basic helix–loop–helix transcription factor
- biomass production
- cell expansion
- delayed flowering