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Chloroplast structure and DNA methylation polymorphisms in an albino mutant of Xinong 1376 wheat (Triticum aestivum L.) cultivar
DNA methylation plays an important role in regulating plant development, including organ and tissue differentiation, which may determine variations in agronomic traits. However, there are no reports on the regulation of leaf color in wheat. To address this issue, the present study investigated the chloroplast structure and epigenetic mechanisms regulating the leaf color in an albino mutant of the Xinong 1376 wheat (Triticum aestivum L.) cultivar. Structural analysis was performed by scanning and transmission electron microscopy, and epigenetic modifications were detected by methylation-sensitive amplification polymorphism (MSAP) analysis. We observed that mesophyll cells of green leaves showed a well-ordered arrangement and were filled with chloroplasts with intact lamellar structures and thylakoid membranes. In contrast, mesophyll cells of red and white leaves were disorganized and contained only a few plastids or chloroplasts with no lamellar structures or thylakoid membranes. Comparison of MSAP profiles revealed that white (red) leaves had higher levels of cytosine methylation (4.35% and 4.10% in red and white leaves, respectively) and showed changes in polymorphic loci as compared with those in green leaves. We sequenced 150 DNA fragments, which were differentially displayed in MSAP patterns of white (red) and green leaves of the Xinong 1376 albino mutant of wheat. A further BLAST search of 77 cloned sequences showed that they were located in coding regions. Interestingly, the majority of these sequences were found to be involved in processes such as signals transduction, transcription regulation, posttranscriptional processing, DNA modification and repair, transport, biosynthesis of cellulose, photosynthesis, protein ubiquitination, stress responses, retroposition. Expression analysis demonstrated a decrease in the transcription of two methylated genes, psaA and psbD, which are involved in the photosystem. Although the DNA methylation changes and leaf color changes were not directly associated, these results may indicate that methylation of specific genes is an active and rapid epigenetic response to the variation of leaf color in the Xinong 1376 albino mutant of wheat, further elucidating the mechanism of variation of the leaf color.
CP17471 Accepted 16 January 2018
© CSIRO 2018