Comparative transcriptome analysis revealed the conversions of stamens into pistil-like structures in Aegilops crassa cytoplasmic male sterile wheat (Triticum aestivum)

Abstract

Background: Aegilops crassa cytoplasm is an essential material for investigating the cytoplasm of cytoplasmic male sterility (CMS). Moreover, the stamens of C303A exhibit a high degree of pistillody, turning almost white. However, the underlying molecular mechanism of C303A pistillody remains unclear. Therefore, to gain a better understanding of C303A, the phenotypic and cytological features of C303A were observed to identify the key stage that the homeotic transformation of stamens into pistil-like structures, transcriptome profiles were determined by Illumina RNA sequencing technology (RNA-Seq) of stamen. Results: Through morphological observation, for CMS wheat with Aegilops crassa cytoplasm (CMS-C) line C303A, the pistil of which developed normally, but stamens were ultimately aborted and the stamens released no pollen when mature. According to the results of the paraffin section, stamens began to transform into pistils or pistil-like structures at binucleate stage (BNS). Therefore, the stamens of line C303A and its maintainer 303B at BNS were collected for transcriptome sequencing. A total of 20,444 wheat genes were detected as being differentially expressed between C303A and 303B stamens, included 10,283 up-regulated and 10,161 down-regulated genes. Gene Ontology Enrichment Analyses showed that most differentially expressed genes (DEGs) distributed on the metabolic process, cell, cellular process, catalytic activity and cell part. From KEGG, we knew that DEGs were mainly enriched to energy metabolism. We also found several essential genes that may contribute to pistillody in C303A. Based on the above analysis, we believe that due to the confusion of energy metabolism and reactive oxygen metabolism, thereby inducing the pistillody and eventually lead to the abortion of C303A. Conclusion:This study unravels the complex transcriptome profiles in C303A stamen, highlighting the energy metabolism and class B MADS-box genes related to pistillody. This work should lay the foundations of future studies in the mechanical response to wheat stamen and pollen development in CMS.