Combined Transcriptome Analysis Reveals the Ovule Abortion Regulatory Mechanisms in the Female Sterile Line of Pinus tabuliformis Carr.

Zaixin Gong,Rui Han,Ming Zeng,Qianquan Yang,Caixia Zheng,Yuanyuan Zhao,Li Xu,Min Zhang,Hailin Hu

doi:10.3390/ijms22063138

Zaixin Gong, Rui Han + Show 7 more

Open Access

https://doi.org/10.3390/ijms22063138

Copy DOI

Abstract

Ovule abortion is a common phenomenon in plants that has an impact on seed production. Previous studies of ovule and female gametophyte (FG) development have mainly focused on angiosperms, especially in Arabidopsis thaliana. However, because it is difficult to acquire information about ovule development in gymnosperms, this remains unclear. Here, we investigated the transcriptomic data of natural ovule abortion mutants (female sterile line, STE) and the wild type (female fertile line, FER) of Pinus tabuliformis Carr. to evaluate the mechanism of ovule abortion during the process of free nuclear mitosis (FNM). Using single-molecule real-time (SMRT) sequencing and next-generation sequencing (NGS), 18 cDNA libraries via Illumina and two normalized libraries via PacBio, with a total of almost 400,000 reads, were obtained. Our analysis showed that the numbers of isoforms and alternative splicing (AS) patterns were significantly variable between FER and STE. The functional annotation results demonstrate that genes involved in the auxin response, energy metabolism, signal transduction, cell division, and stress response were differentially expressed in different lines. In particular, AUX/IAA, ARF2, SUS, and CYCB had significantly lower expression in STE, showing that auxin might be insufficient in STE, thus hindering nuclear division and influencing metabolism. Apoptosis in STE might also have affected the expression levels of these genes. To confirm the transcriptomic analysis results, nine pairs were confirmed by quantitative real-time PCR. Taken together, these results provide new insights into ovule abortion in gymnosperms and further reveal the regulatory mechanisms of ovule development.

Highlights

IntroductionSexual reproduction is the most evolved reproductive mode in plants, as well as a step in the life cycle of seed plants
The differences of the cone and ovule phenotypes of P. tabuliformis between fertile line (FER) and sterile line (STE) occurred from the FMN2 stage, and the development of female gametophyte (FG) was blocked in STE
The low expression of differentially expressed genes (DEGs) related to auxin response in STE might lead to insufficient energy supply and nuclear division damage, which might be another reason for the scales being bigger in STE

Summary

Introduction

Sexual reproduction is the most evolved reproductive mode in plants, as well as a step in the life cycle of seed plants. The completion of sexual reproduction depends on the normal development of reproductive organs and embryos. Female sterility is a common phenomenon during sexual reproduction in the plant kingdom [1,2], which might result in yield reduction, affect fine variety breeding, and decrease the economic benefit of agronomically important crops and woody plants. Female sterility may be induced by many factors, such as abnormal ovule development, the wrong number of polar nuclei, meiosis, and mitotic disorder. Female sterile mutants of Punica granatum L

Methods

Results

Discussion

Conclusion