Ethylene controls cambium stem cell activity via promoting local auxin biosynthesis

Authors: YU, QIN - China Agricultural University; CHENG, CHENXIA - China Agricultural University; ZHOU, XIAOFENG - China Agricultural University; LI, YONGHONG - China Agricultural University; HU, YINGCHUN - China Agricultural University; YANG, CHUN - China Agricultural University; ZHOU, YINGYING - China Agricultural University; SOLIMAN, TAREK M.A. - China Agricultural University; ZHANG, HAO - China Agricultural University; WANG, QIGANG - China Agricultural University; WANG, HUICHUN - China Agricultural University; Jiang, Cai-Zhong; GAN, SHU-SHENG - Cornell University; GAO, JUNPING - China Agricultural University; MA, NAN - China Agricultural University

Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2023
Publication Date: 6/4/2023
Citation: Yu, Q., Cheng, C., Zhou, X., Li, Y., Hu, Y., Yang, C., Zhou, Y., Soliman, T., Zhang, H., Wang, Q., Wang, H., Jiang, C., Gan, S., Gao, J., Ma, N. 2023. Ethylene controls cambium stem cell activity via promoting local auxin biosynthesis. New Phytologist. 239(3):964-978. https://doi.org/10.1111/nph.19004.
DOI: https://doi.org/10.1111/nph.19004

Interpretive Summary: Plant phytohormones play diverse roles in regulating plant growth and development. The vascular cambium is the main secondary meristem in plants that produces secondary phloem (outside) and xylem (inside) on opposing sides of the cambium. This process is responsible for alterations of the diameter of stems and roots and for forming woody tissue. The phytohormone ethylene has been implicated in vascular cambium activity, but the regulatory network underlying ethylene-mediated cambial activity remains to be elucidated. In this study, we found that PETAL MOVEMENT-RELATED PROTEIN1 (RhPMP1), an ethylene-inducible HOMEODOMAIN-LEUCINE ZIPPER I transcription factor in woody plant rose (Rosa hybrida), regulates local auxin biosynthesis and auxin transport to maintain cambial activity. Knockdown of RhPMP1 resulted in smaller midveins and reduced auxin content, while RhPMP1 overexpression resulted in larger midveins and increased auxin levels compared to the wild-type plants. Further, we revealed that Indole-3-pyruvate monooxygenase YUCCA 10 (RhYUC10) and Auxin transporter-like protein 2 (RhAUX2), encoding an auxin biosynthetic enzyme and an auxin influx carrier, respectively, are direct downstream targets of RhPMP1. Our results demonstrate that ethylene promotes an auxin maximum in the cambium adjacent to the xylem to maintain cambial activity in plants.

Technical Abstract: The vascular cambium is the main secondary meristem in plants that produces secondary phloem (outside) and xylem (inside) on opposing sides of the cambium. The phytohormone ethylene has been implicated in vascular cambium activity, but the regulatory network underlying ethylene-mediated cambial activity remains to be elucidated. In this study, we found that PETAL MOVEMENT-RELATED PROTEIN1 (RhPMP1), an ethylene-inducible HOMEODOMAIN-LEUCINE ZIPPER I transcription factor in woody plant rose (Rosa hybrida), regulates local auxin biosynthesis and auxin transport to maintain cambial activity. Knockdown of RhPMP1 resulted in smaller midveins and reduced auxin content, while RhPMP1 overexpression resulted in larger midveins and increased auxin levels compared to the wild-type plants. Further, we revealed that Indole-3-pyruvate monooxygenase YUCCA 10 (RhYUC10) and Auxin transporter-like protein 2 (RhAUX2), encoding an auxin biosynthetic enzyme and an auxin influx carrier, respectively, are direct downstream targets of RhPMP1. Our results suggest that ethylene promotes an auxin maximum in the cambium adjacent to the xylem to maintain cambial activity.