Heterosis analysis and underlying molecular regulatory mechanism in a wide-compatible neo-tetraploid rice line with long panicles

Abstract

Background: Neo-tetraploid rice, which is a new germplasm developed from autotetraploid rice, has a powerful biological and yield potential and could be used for commercial utilization. The length of panicle, as a part of rice panicle architecture, contributes greatly to high yield. However, little information about long panicle associated with heterosis or hybrid vigor is available in neo-tetraploid rice. Results: In the present study, we developed a neo-tetraploid rice line, Huaduo 8 (H8), with long panicles and harboring wide-compatibility genes for pollen and embryo sac fertility. All the hybrids generated by H8 produced significant high-parent yield heterosis and displayed long panicles similar to H8. RNA-seq analysis detected a total of 4013, 7050, 6787 and 6195 differentially expressed genes uniquely belonging to F 1 and specifically (DEGFu-sp) associated with leaf, sheath, main panicle axis and spikelet in the two hybrids, respectively. Of these DEGFu-sp, 279 and 89 genes were involved in kinase and synthase, and 714 cloned genes, such as GW8, OsGA20ox1, Ghd8, GW6a, and LP1, were identified and validated by qRT-PCR. A total of 2925 known QTLs intervals, with an average of 1~100 genes per interval, were detected in both hybrids. Of these, 109 yield-related QTLs were associated with seven important traits in rice. Moreover, 1393 non-additive DEGs, including 766 up-regulated and 627 down-regulated, were detected in both hybrids. Importantly, eight up-regulated genes associated with panicle were detected in young panicles of the two hybrids compared to their parents by qRT-PCR. Re-sequencing analysis depicted that LP (a gene controlling long panicle) sequence of H8 was different from many other neo-tetraploid rice and most of the diploid and autotetraploid lines. The qRT-PCR results showed that LP was up-regulated in the hybrid compared to its parents at very young stage of panicle development. Conclusions: These results suggested that H8 could overcome the intersubspecific autotetraploid hybrid rice sterility caused by embryo sac and pollen sterility loci. Notably, long panicles of H8 showed dominance phenomenon and played an important role in yield heterosis, which is a complex molecular mechanism. The neotetraploid rice is a useful germplasm to attain high yield of polyploid rice.

iTRAQ-Based Quantitative Glutelin Proteomic Analysis Reveals Differentially Expressed Proteins in the Physiological Metabolism Process during Endosperm Development and their Impacts on Yield and Quality in Autotetraploid Rice

“…The grains were labeled at the time of owering, collected 5,6,7,8,9,10,11,12,15,18,20,21, and 24 DAF and stored at -80 °C in a freezer.…”

“…As a basic feature in nearly all plant species, polyploidization normally results in a higher yield than that of diploid plants and is regarded as a powerful tool in crop breeding (Ramanna and Jacobsen 2003). During the last decade, the application of polyploidization has been used in rice breeding, and several highly productive hybrid rice lines have been developed (Cai et al 2007;He et al 2011;Ghaleb et al 2020). Through comparative studies between diploid and autotetraploid rice cultivars, it was shown that there are higher glutelin contents in autotetraploid cultivars than in diploid cultivars (Cai 2011).…”

Comparative cytological and transcriptome analysis reveals high pollen fertility and upregulation of environmentally sensitive genic male sterility genes in neo-tetraploid rice

“…Knock-out of environmentally sensitive genic male sterility genes causes pollen abortion in neo-tetraploid rice Neo-tetraploid rice is a key step to overcome the sterility of F 1 hybrids in autotetraploid rice (Guo et al 2017;Bei et al 2019;Ghaleb et al 2020). To verify the up-regulation of pollen fertility gene play the important role in neo-tetraploid rice, we used CRISPR/cas9 technology to conduct the study.…”

“…It is great demand to reveal the mechanism of its low pollen fertility and acquired the high pollen fertility tetraploid materials. After years of efforts, we successfully developed a new "autotetraploid rice lines" by selective breeding and crossing for successive generations (Guo et al 2017;Bei et al 2019; Ghaleb et al 2020). The new "autotetraploid rice" displayed high fertility (>80%) and high heterosis while crossed with other autotetraploid rice lines having low fertility (Guo et al 2017;Chen et al 2018;Bei et al 2019).…”

iTRAQ-Based Quantitative Glutelin Proteomic Analysis Reveals Differentially Expressed Proteins in Physiological Metabolism Process during Endosperm Development and their Impacts on Yield and Quality in Autotetraploid Rice

“…During the last decade, the application of polyploidization has been used in rice breeding, and several highly productive hybrid rice lines have been developed (Cai et al 2007;He et al 2011;Ghaleb et al 2020). Through comparative studies between diploid and autotetraploid rice cultivars, it was shown that there are higher glutelin contents in autotetraploid cultivars than in diploid cultivars (Cai 2011).…”