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Plant function and evolutionary biology
RESEARCH ARTICLE

Biochemical and transcriptomic analysis of maize diversity to elucidate drivers of leaf carbon isotope composition

Allison R. Kolbe A , Anthony J. Studer B and Asaph B. Cousins A C
+ Author Affiliations
- Author Affiliations

A School of Biological Sciences, PO Box 644236, Washington State University, Pullman, WA 99164, USA.

B Department of Crop Sciences, 1201 West Gregory Drive, Edward R. Madigan Laboratory 289, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA.

C Corresponding author. Email: acousins@wsu.edu

Functional Plant Biology 45(5) 489-500 https://doi.org/10.1071/FP17265
Submitted: 8 July 2017  Accepted: 1 November 2017   Published: 11 December 2017

Abstract

Carbon isotope discrimination is used to study CO2 diffusion, substrate availability for photosynthesis, and leaf biochemistry, but the intraspecific drivers of leaf carbon isotope composition (δ13C) in C4 species are not well understood. In this study, the role of photosynthetic enzymes and post-photosynthetic fractionation on δ13C (‰) was explored across diverse maize inbred lines. A significant 1.3‰ difference in δ13C was observed between lines but δ13C did not correlate with in vitro leaf carbonic anhydrase (CA), phosphoenolpyruvate carboxylase (PEPC), or ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity. RNA-sequencing was used to identify potential differences in post-photosynthetic metabolism that would influence δ13C; however, no correlations were identified that would indicate significant differences in post-photosynthetic fractionation between lines. Variation in δ13C has been observed between C4 subtypes, but differential expression of NADP-ME and PEP-CK pathways within these lines did not correlate with δ13C. However, co-expression network analysis provided novel evidence for isoforms of C4 enzymes and putative transporters. Together, these data indicate that diversity in maize δ13C cannot be fully explained by variation in CA, PEPC, or Rubisco activity or gene expression. The findings further emphasise the need for future work exploring the influence of stomatal sensitivity and mesophyll conductance on δ13C in maize.

Additional keywords: C4 photosynthesis, leaf carbon isotope composition, photosynthetic enzymes, RNA-seq, Zea mays.


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