Abstract
Double fertilization is a key determinant of grain yield, and the failure of fertilization during hybridization is one important reason for reproductive isolation. Therefore, fertilization has a very important role in the production of high-yield and well-quality hybrid of rice. Here, we used RNA sequencing technology to study the change of the transcriptome during double fertilization with the help of the mutant fertilization barrier (feb) that failed to finish fertilization process and led to seed abortion. The results showed that 1669 genes were related to the guided growth of pollen tubes, 332 genes were involved in the recognition and fusion of the male–female gametes, and 430 genes were associated with zygote formation and early free endosperm nuclear division. Among them, the genes related to carbohydrate metabolism; signal transduction pathways were enriched in the guided growth of pollen tubes, the genes involved in the photosynthesis; fatty acid synthesis pathways were activated by the recognition and fusion of the male–female gametes; and the cell cycle-related genes might play an essential role in zygote formation and early endosperm nuclear division. Furthermore, among the 1669 pollen tube-related genes, it was found that 7 arabinogalactan proteins (AGPs), 1 cysteine-rich peptide (CRP), and 15 receptor-like kinases (RLKs) were specifically expressed in anther, while 2 AGPs, 7 CRPs, and 5 RLKs in pistil, showing obvious unequal distribution which implied they might play different roles in anther and pistil during fertilization. These studies laid a solid foundation for revealing double fertilization mechanism of rice and for the follow-up investigation.
Highlights
In angiosperms, female gamete is embraced in the multicellular ovule, while the male gametes produce in another tissue-anther
The ovary transparency assay showed that the development of the pistil in feb was similar to WT while remained unfertilized at 8 hour after pollination (HAP) (Figures 1 and 2)
The analysis of RNA sequencing (RNA-seq) and the principal component analysis (PCA) showed that the transcriptome of M1 (1–20 min after pollination in feb) was similar to N1 (1–20 min after pollination in WT) while the transcriptome of M3 (8 HAP in feb) was similar to N2
Summary
Female gamete is embraced in the multicellular ovule, while the male gametes produce in another tissue-anther. The nonmotile sperm cells are delivered to the female gametophyte (embryo sac) by the elongated pollen tube. This is a long and complex process, and is precisely regulated by a range of genes. One sperm cell fuses with an egg cell to form a fertilized egg cell (zygote), while the other fuses with a central cell with two polar nuclei to form the primary endosperm nucleus, which is called double fertilization in angiosperms [1] The former develops as an embryo, while the latter forms endosperm, which is the main part of seed in cereal. The success of the process plays a crucial role for high grain yield
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