Insights into transcriptional characteristics and homoeolog expression bias of embryo and de-embryonated kernels in developing grain through RNA-Seq and Iso-Seq
Bread wheat (Triticum aestivum L.) is an allohexaploid, and the transcriptional characteristics of the wheat embryo and endosperm during grain development remain unclear. To analyze the transcriptome, we performed isoform sequencing (Iso-Seq) for wheat grain and RNA sequencing (RNA-Seq) for the embryo and de-embryonated kernels. The differential regulation between the embryo and de-embryonated kernels was found to be greater than the difference between the two time points for each tissue. Exactly 2264 and 4790 tissue-specific genes were found at 14 days post-anthesis (DPA), while 5166 and 3784 genes were found at 25 DPA in the embryo and de-embryonated kernels, respectively. Genes expressed in the embryo were more likely to be related to nucleic acid and enzyme regulation. In de-embryonated kernels, genes were rich in substance metabolism and enzyme activity functions. Moreover, 4351, 4641, 4516, and 4453 genes with the A, B, and D homoeoloci were detected for each of the four tissues. Expression characteristics suggested that the D genome may be the largest contributor to the transcriptome in developing grain. Among these, 48, 66, and 38 silenced genes emerged in the A, B, and D genomes, respectively. Gene ontology analysis showed that silenced genes could be inclined to different functions in different genomes. Our study provided specific gene pools of the embryo and de-embryonated kernels and a homoeolog expression bias model on a large scale. This is helpful for providing new insights into the molecular physiology of wheat.
KeywordsAlternative splicing Grain development Homoeologous gene Transcriptome Wheat
We thank 1GENE Technologies Company for technology support (Hangzhou, China).
YXL designed the research. HC and JHZ performed embryo and endosperm collection and RNA extractions. JW and JDL performed the RNA-Seq analysis and data analysis. JW and YF performed the quantitative RT-PCR. JW and YXL wrote the manuscript. CTL, RZS, JDL, and WLL participated in the interpretation and discussion of results, and contributed to the writing of the paper.
This work was financially supported by the Chinese Academy of Sciences grant (XDA08010303), the National Key Research and Development Program of China (2018YFD0100901), and the National Natural Science Foundation of China (31371242) to YL.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
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