A co-opted steroid synthesis gene, maintained in sorghum but not maize, is associated with a divergence in leaf wax chemistry

Lucas Busta, Elizabeth Schmitz, Dylan K. Kosma, James C. Schnable, Edgar B. Cahoon

Research output: Contribution to journalArticlepeer-review


Virtually all land plants are coated in a cuticle, a waxy polyester that prevents nonstomatal water loss and is important for heat and drought tolerance. Here, we describe a likely genetic basis for a divergence in cuticular wax chemistry between Sorghum bicolor, a drought tolerant crop widely cultivated in hot climates, and its close relative Zea mays (maize). Combining chemical analyses, heterologous expression, and comparative genomics, we reveal that: 1) sorghum and maize leaf waxes are similar at the juvenile stage but, after the juvenile-to-adult transition, sorghum leaf waxes are rich in triterpenoids that are absent from maize; 2) biosynthesis of the majority of sorghum leaf triterpenoids is mediated by a gene that maize and sorghum both inherited from a common ancestor but that is only functionally maintained in sorghum; and 3) sorghum leaf triterpenoids accumulate in a spatial pattern that was previously shown to strengthen the cuticle and decrease water loss at high temperatures. These findings uncover the possibility for resurrection of a cuticular triterpenoid-synthesizing gene in maize that could create a more heat-tolerant water barrier on the plant’s leaf surfaces. They also provide a fundamental understanding of sorghum leaf waxes that will inform efforts to divert surface carbon to intracellular storage for bioenergy and bioproduct innovations.

Original languageEnglish (US)
Article numbere2022982118
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number12
StatePublished - Mar 23 2021
Externally publishedYes

Bibliographical note

Funding Information:
ACKNOWLEDGMENTS. We thank Samantha Link for the highest quality assistance with growing sorghum plants, Dr. Ignacio A. Ciampitti at Kansas State University for permission to reproduce with alteration his image “Sorghum Growth and Development,” and the Holland Computing Center at the University of Nebraska–Lincoln for computing resources. We are also grateful to Rebecca E. Cahoon for providing comments on a draft of this manuscript. L.B. would like to thank E.B.C. as well as David R. Holding and Chi Zhang for their mentorship. L.B. acknowledges support in the form of a fellowship from the NSF Plant Genome Research Program (NSF PRFB IOS-1812037). E.S. was supported by funding from the NSF (Grant OIA-1557417). E.B.C. acknowledges support from the U.S. Department of Energy Center for Advanced Bioenergy and Bioproducts Innovation (Award DE-SC0018420) for sorghum feedstock improvement.

Publisher Copyright:
© 2021 National Academy of Sciences. All rights reserved.


  • Cuticular wax | drought tolerance | triterpenoids | juvenile-to-adult transition | sorghum bicolor

PubMed: MeSH publication types

  • Journal Article

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