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

Authors

• Lucas Busta, University of Nebraska - LincolnFollow
• Elizabeth Schmitz, University of Nebraska-Lincoln
• Dylan K. Kosma, University of Nevada, RenoFollow
• James Schnable, University of Nebraska-LincolnFollow
• Edgar B. Cahoon, University of Nebraska - LincolnFollow

ORCID IDs

Lucas Busta https://orcid.org/0000-0002-0102-9986

Elizabeth Schmitz https://orcid.org/0000-0002-9619-5193

Dylan K. Kosma https://orcid.org/0000-0002-6880-7260

James C. Schnable https://orcid.org/0000-0001-6739-5527

Edgar B. Cahoon https://orcid.org/0000-0002-7277-1176

Document Type

Article

Date of this Version

3-15-2021

Citation

PNAS 2021 Vol. 118 No. 12 e2022982118

https://doi.org/10.1073/pnas.2022982118

Comments

Creative Commons Attribution-NonCommercial- NoDerivatives License 4.0 (CC BY-NC-ND).

Abstract

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.