棉纤维发育的基因组分析和基因表达谱

The goals of our cotton research program are to understand fiber developmental biology and improve fiber production using molecular and genomic tools. In the genome mapping project,we have developed a cotton genetic map using a moderate set of AFLP, SSR, and RFLP markers. Polymorphism was detected in two polyploid cotton cultivars, G. hirsutum L. var. ……

An Epigenetic Role for Disrupted Paternal Gene Expression in Postzygotic Seed Abortion in Arabidopsis Interspecific Hybrids

Interspecific hybrids often increase the levels of heterozygosity and hybrid vigor, but some interspecific hybrid seeds are aborted shortly after fertilization. The mechanism behind this postzygotic seed abortion is poorly understood. Here, we report genome-wide analysis of allelic expression changes in developing siliques and seeds in three F1 interspecific crosses between Arabidopsis thaliana （Col, Ler, or C24） and Arabidopsis arenosa. The majority of maternally expressed genes （MEGs） were shared among all three F1 interspecific crosses, whereas ~90% of 272 paternally expressed genes （PEGs） were found only in one or two F1 crosses, suggesting a role for disrupted paternal gene expression in seed abortion that varies in different crosses. Consistent with this notion, 12 PEGs in the infertile interspecific hybrids matched MEGs in fertile intraspecific hybrids. This disruption of PEGs in the interspecific hybrids was consistent with the upregulation of the genes in the paternal-excess interploidy cross （2X6） between a diploid mother and a hexaploid father, leading to the seed abortion. Moreover, a subset of PEGs in the interspecific crosses were also upregulated in the intraspecific hybrid metlXWT or meaXWT, in which the mutant of MET1 （DNA METHYL TRANSFERASE1） or MEDEA, a Polycomb Repressive Complex2 gene, was used as the maternal parent. These data suggest that maternal epigenetic factors and paternal gene expression play important roles in the postzygotic seed abortion in interspecific hybrids or neo-allopolyploids.

Rice Interploidy Crosses Disrupt Epigenetic Regulation, Gene Expression, and Seed Development

Seed development in angiosperms requires a 2：1 maternal-to-paternal genome ratio （2m：lp） in the endo- sperm. When the ratio is disrupted, the seed development is impaired. Rice interploidy crosses result in endosperm failures, but the underlying molecular mechanisms remain unclear. Here, we report that the defective endosperm in rice interploidy crosses was associated with nonadditive expression of small RNAs and protein-coding genes. Interestingly, 24-nt small interfering RNAs were enriched in the 5＇ and 3＇ flanking sequences of nonadditively expressed genes in the interploidy crosses and were negatively associated with the expression of imprinted genes. Furthermore, some PRC2 family genes and DNA methylaUon-related genes including OsMETlb and OsCMT3a were upregulated in the 2x4 cross （polli- nating a diploid ＂mother＂ with a tetraploid ＂father＂） but repressed in the reciprocal cross. These different epigenetic effects could lead to precocious or delayed cellularization during endosperm development. Notably, many endosperm-preferred genes, including starch metabolic and storage protein genes during grain filling, were found to be associated with DNA methylation or H3K27me3, which are repressed in both 2×4 and 4 ×2 crosses. WUSCHEL homeobox2 （WOX2）-Iike （WOX2L）, an endosperm-preferred gene, was expressed specifically in the rice endosperm, in contrast to WOX2 expression in the Arabidopsis embryo. Disruption of WOX2L in transgenic rice by CRISPR/Cas9-mediated gene editing blocked starch and protein accumulation, resulting in seed abortion. In addition to gene repression, disrupting epigenetic process in the interploidy crosses also induced expression of stress-responsive genes. Thus, maintaining the 2m：lp genome ratio in the endosperm is essential for normal grain development in rice and other cereal crops.