Jinsu Lee1, Seahee Han2, Hwa-Yong Lee1, Bomi Jeong3, Tae-Young Heo3, Tae Kyung Hyun4, Kyunghwan Kim1, Byoung Il Je5, Horim Lee6, Donghwan Shim7, Soon Ju Park8, Hojin Ryu9. 1. Department of Biology, Chungbuk National University, Cheongju, 28644, Republic of Korea. 2. National Agrobiodiversity Center, National Academy of Agricultural Science RDA, Jeonju, 54875, Republic of Korea. 3. Department of Information and Statistics, Chungbuk National University, Cheongju, 28644, Republic of Korea. 4. Department of Industrial Plant Science and Technology, Chungbuk National University, Cheongju, 28644, Republic of Korea. 5. Department of Horticultural Bioscience, College of Natural Resource and Life Science, Pusan National University, Miryang, 50467, Republic of Korea. 6. Department of Biotechnology, Duksung Women's University, Seoul, 01369, Republic of Korea. 7. Department of Forest Bio-Resources, National Institute of Forest Science, Suwon, 16631, Republic of Korea. 8. Division of Biological Sciences, Research Institute for Basic Science, Wonkwang University, Iksan, 54538, Republic of Korea. 9. Department of Biology, Chungbuk National University, Cheongju, 28644, Republic of Korea. hjryu96@gmail.com.
Abstract
MAIN CONCLUSION: BR signaling pathways facilitate xylem differentiation and wood formation by fine tuning SlBZR1/SlBZR2-mediated gene expression networks involved in plant secondary growth. Brassinosteroid (BR) signaling and BR crosstalk with diverse signaling cues are involved in the pleiotropic regulation of plant growth and development. Recent studies reported the critical roles of BR biosynthesis and signaling in vascular bundle development and plant secondary growth; however, the molecular bases of these roles are unclear. Here, we performed comparative physiological and anatomical analyses of shoot morphological growth in a cultivated wild-type tomato (Solanum lycopersicum cv. BGA) and a BR biosynthetic mutant [Micro Tom (MT)]. We observed that the canonical BR signaling pathway was essential for xylem differentiation and sequential wood formation by facilitating plant secondary growth. The gradual retardation of xylem development phenotypes during shoot vegetative growth in the BR-deficient MT tomato mutant recovered completely in response to exogenous BR treatment or genetic complementation of the BR biosynthetic DWARF (D) gene. By contrast, overexpression of the tomato Glycogen synthase kinase 3 (SlGSK3) or CRISPR-Cas9 (CR)-mediated knockout of the tomato Brassinosteroid-insensitive 1 (SlBRI1) impaired BR signaling and resulted in severely defective xylem differentiation and secondary growth. Genetic modulation of the transcriptional activity of the tomato Brassinazole-resistant 1/2 (SlBZR1/SlBZR2) confirmed the positive roles of BR signaling pathways for xylem differentiation and secondary growth. Our data indicate that BR signaling pathways directly promote xylem differentiation and wood formation by canonical BR-activated SlBZR1/SlBZR2.
MAIN CONCLUSION: BR signaling pathways facilitate xylem differentiation and wood formation by fine tuning SlBZR1/SlBZR2-mediated gene expression networks involved in plant secondary growth. Brassinosteroid (BR) signaling and BR crosstalk with diverse signaling cues are involved in the pleiotropic regulation of plant growth and development. Recent studies reported the critical roles of BR biosynthesis and signaling in vascular bundle development and plant secondary growth; however, the molecular bases of these roles are unclear. Here, we performed comparative physiological and anatomical analyses of shoot morphological growth in a cultivated wild-type tomato (Solanum lycopersicum cv. BGA) and a BR biosynthetic mutant [Micro Tom (MT)]. We observed that the canonical BR signaling pathway was essential for xylem differentiation and sequential wood formation by facilitating plant secondary growth. The gradual retardation of xylem development phenotypes during shoot vegetative growth in the BR-deficient MT tomato mutant recovered completely in response to exogenous BR treatment or genetic complementation of the BR biosynthetic DWARF (D) gene. By contrast, overexpression of the tomato Glycogen synthase kinase 3 (SlGSK3) or CRISPR-Cas9 (CR)-mediated knockout of the tomato Brassinosteroid-insensitive 1 (SlBRI1) impaired BR signaling and resulted in severely defective xylem differentiation and secondary growth. Genetic modulation of the transcriptional activity of the tomato Brassinazole-resistant 1/2 (SlBZR1/SlBZR2) confirmed the positive roles of BR signaling pathways for xylem differentiation and secondary growth. Our data indicate that BR signaling pathways directly promote xylem differentiation and wood formation by canonical BR-activated SlBZR1/SlBZR2.
Authors: Fabiola Ramirez-Torres; Rishikesh Ghogare; Evan Stowe; Pedro Cerdá-Bennasser; Maria Lobato-Gómez; Bruce A Williamson-Benavides; Patricia Sarai Giron-Calva; Seanna Hewitt; Paul Christou; Amit Dhingra Journal: Transgenic Res Date: 2021-04-06 Impact factor: 3.145