Comparative Proteomic Analysis of the Response of Maize (Zea mays L.) Leaves to Long Photoperiod Condition.

Liuji Wu,Shunxi Wang,Jun Zhang,Yanhui Chen,Huimin Zhang,Zhiqiang Tian,Haiping Liu,Lei Tian,Ping Liu

doi:10.3389/fpls.2016.00752

Liuji Wu, Shunxi Wang + Show 7 more

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https://doi.org/10.3389/fpls.2016.00752

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Abstract

Maize (Zea mays L.), an important industrial material and food source, shows an astonishing environmental adaptation. A remarkable feature of its post-domestication adaptation from tropical to temperate environments is adaptation to a long photoperiod (LP). Many photoperiod-related genes have been identified in previous transcriptomics analysis, but proteomics shows less evidence for this mechanism of photoperiod response. In this study, we sampled newly expanded leaves of maize at the three- and six-leaf stages from an LP-sensitive introgression line H496, the donor CML288, LP-insensitive inbred line, and recurrent parent Huangzao4 (HZ4) grown under long days (15 h light and 9 h dark). To characterize the proteomic changes in response to LP, the iTRAQ-labeling method was used to determine the proteome profiles of plants exposed to LP. A total of 943 proteins differentially expressed at the three- and six-leaf stages in HZ4 and H496 were identified. Functional analysis was performed by which the proteins were classified into stress defense, signal transduction, carbohydrate metabolism, protein metabolism, energy production, and transport functional groups using the WEGO online tool. The enriched gene ontology categories among the identified proteins were identified statistically with the Cytoscape plugin ClueGO + Cluepedia. Twenty Gene Ontology terms showed the highest significance, including those associated with protein processing in the endoplasmic reticulum, splicesome, ribosome, glyoxylate, dicarboxylate metabolism, L-malate dehydrogenase activity, and RNA transport. In addition, for subcellular location, all proteins showed significant enrichment of the mitochondrial outer membrane. The sugars producted by photosynthesis in plants are also a pivotal metabolic output in the circadian regulation. The results permit the prediction of several crucial proteins to photoperiod response and provide a foundation for further study of the influence of LP treatments on the circadian response in short-day plants.

Highlights

Maize (Zea mays L.) is a key food source and industrial material that has rapidly spread in cultivation since originating in Southern Mexico 6000–10,000 years ago from Balsas teosinte (Zea mays ssp. parviglumis; Matsuoka et al, 2002)
To examine the protein changes response to the photoperiod in maize leaves, plant phenotypes were periodically observed in the two inbred lines HZ4 and H496 under long photoperiod (LP) at the three- and sixleaf stages, and the individual samples were collected
We observed that the shoot apical meristem was elongated in the six-leaf stage in both HZ4 and H496 inbred lines (Figures 1E–H), which proved that plants were in different developmental phases at the three- and six-leaf stages

Summary

Introduction

Maize (Zea mays L.) is a key food source and industrial material that has rapidly spread in cultivation since originating in Southern Mexico 6000–10,000 years ago from Balsas teosinte (Zea mays ssp. parviglumis; Matsuoka et al, 2002). In the model plant Arabidopsis thaliana, numerous components associated with the plant circadian clock and photoperiod have been studied to understand the regulation and molecular mechanism of flowering in higher plant (Matsubara et al, 2008; Kumimoto et al, 2010; Lazakis et al, 2011; Knuesting et al, 2015). Only a small number of genes such as ZCN1, ZCN8, and conzl identified by the Arabidopsis orthologues AtTFL1, AtFT, and AtCO, respectively (Danilevskaya et al, 2008; Matsubara et al, 2008; Miller et al, 2008; Lazakis et al, 2011), have been shown to be involved in the regulation of flowering time and the vegetative to reproductive transition in maize.

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