College of Agronomy, Northwest A & F University, Yangling, 712100, China.
BMC Genomics. 2020 Feb 4;21(1):124. doi: 10.1186/s12864-020-6450-2.
Aegilops crassa cytoplasm is an important source for investigating cytoplasmic male sterility (CMS). Moreover, the stamens of line C303A exhibit a high degree of pistillody, turning almost white. However, the molecular mechanism that underlies pistillody in C303A remains unclear. Therefore, to obtain a better understanding of pistillody in C303A, the phenotypic and cytological features of C303A were observed to identify the key stage for the homeotic transformation of stamens into pistil-like structures. Transcriptome profiles were determined for stamens using Illumina RNA sequencing.
Morphological observations of the CMS wheat line with Aegilops crassa cytoplasm C303A showed that the pistils developed normally, but the stamens were ultimately aborted and they released no pollen when mature. According to paraffin section observations, the stamens began to transform into pistils or pistil-like structures in the binucleate stage (BNS). Therefore, the stamens were collected from line C303A and its maintainer 303B in the BNS for transcriptome sequencing. In total, 20,444 wheat genes were determined as differentially expressed in C303A and 303B stamens, with 10,283 upregulated and 10,161 downregulated genes. Gene Ontology enrichment analyses showed that most of the differentially expressed genes (DEGs) were annotated with GO terms comprising metabolic process, cell, cellular process, catalytic activity, and cell part. Analysis based on the Kyoto Encyclopedia of Genes and Genomes database showed that the enriched DEGs were mainly associated with energy metabolism. We also found several essential genes that may contribute to pistillody in C303A. These findings suggest that disrupted energy metabolism and reactive oxygen metabolism induce pistillody and eventually lead to abortion in C303A.
We determined the complex transcriptome profiles for C303A stamens and demonstrated that disrupted energy metabolism and class B MADS-box genes are related to pistillody. These findings may facilitate future studies of the mechanistic response of the wheat stamen and pollen development in CMS.
粗山羊草细胞质是研究细胞质雄性不育（CMS）的重要来源。此外，C303A 品系的雄蕊表现出高度的雌蕊化，几乎变成白色。然而，C303A 中雌蕊化的分子机制尚不清楚。因此，为了更好地理解 C303A 中的雌蕊化，观察了 C303A 的表型和细胞学特征，以确定雄蕊同源转化为雌蕊状结构的关键阶段。使用 Illumina RNA 测序确定了 C303A 雄蕊的转录组图谱。
对含有粗山羊草细胞质的 CMS 小麦品系 C303A 的形态观察表明，雌蕊发育正常，但雄蕊最终败育，成熟时不释放花粉。根据石蜡切片观察，在双核期（BNS），雄蕊开始转化为雌蕊或雌蕊状结构。因此，从 C303A 及其保持系 303B 的 BNS 中收集雄蕊进行转录组测序。总共鉴定出 20444 个在 C303A 和 303B 雄蕊中差异表达的小麦基因，其中 10283 个上调，10161 个下调。GO 富集分析表明，大多数差异表达基因（DEGs）被注释为代谢过程、细胞、细胞过程、催化活性和细胞部分。基于京都基因与基因组百科全书数据库的分析表明，富集的 DEGs 主要与能量代谢有关。我们还发现了一些可能导致 C303A 雌蕊化的关键基因。这些发现表明，能量代谢和活性氧代谢的破坏导致 C303A 中的雌蕊化，最终导致败育。
我们确定了 C303A 雄蕊的复杂转录组图谱，并表明能量代谢和 B 类 MADS 框基因的破坏与雌蕊化有关。这些发现可能有助于未来研究 CMS 中小麦雄蕊和花粉发育的机制反应。
