Begomoviruses are single-stranded DNA viruses and cause severe diseases in major crop plants worldwide. Based on current genome sequence analyses, we found that synonymous codon usage variations in the protein-coding ...Begomoviruses are single-stranded DNA viruses and cause severe diseases in major crop plants worldwide. Based on current genome sequence analyses, we found that synonymous codon usage variations in the protein-coding genes of begomoviruses are mainly influenced by mutation bias. Base composition analysis suggested that the codon usage bias of AV1 and BV1 genes is significant and their expressions are high. Fourteen codons were determined as translational optimal ones according to the comparison of codon usage patterns between highly and lowly expressed genes. Interestingly the codon usages between begomoviruses from the Old and the New Worlds are apparently different, which supports the idea that the bipartite begomoviruses of the New World might originate from bipartite ones of the Old World, whereas the latter evolve from the Old World monopartite begomoviruses.展开更多
In eukaryotes, a protein motif consisting of WG/GW repeats, also called the Argonaute （AGO） hook, is thought to be essential for binding AGO proteins to fulfill their functions in RNA-mediated gene silencing. Althou...In eukaryotes, a protein motif consisting of WG/GW repeats, also called the Argonaute （AGO） hook, is thought to be essential for binding AGO proteins to fulfill their functions in RNA-mediated gene silencing. Although a number of WG/GW-containing proteins have been computationally identified in Arabidopsis, their roles in plant growth and development are unknown. Here, we show that the Arabidopsis Suppressor of Ty insertion 6-like （SPT6L） gene, which encodes a protein with C-terminal WG/GW repeats, plays critical roles in embryonic development. SPT6L is evolutionarily conserved only in vascular plants, with varying numbers of C-terminal WG/GW repeats, which are plant-species specific. spt61 mutants formed embryos with an aberrant apical-basal axis, showing insufficient development of the basal domain and embryonic lethality. Expression domains of the class-Ill homeodomain-leucine zipper （HD-ZIP III） genes PHABULOSA （PHB） and PHAVOLUTA （PHV） were expanded in the spt61 embryo. In contrast, the PLETHORA1 （PLT1） gene, which acts antagonistically to the HD-ZIP III genes in specification of basal fate, was severely down-regulated in the spt61 mutant. Furthermore, the phb phv double mutations partially rescued aberrant basal development in the spt61 background and restored PLT1 expression. Collectively, our results indicate that SPT6L is essential for specification of the apical-basal axis, partly by controlling the HD-ZIP III genes in embryos.展开更多
基金the National Basic Research and Development Program (973) of China (No. 2006CB101903)the National Excellent Doctoral Dissertation of China (No. 200768)
文摘Begomoviruses are single-stranded DNA viruses and cause severe diseases in major crop plants worldwide. Based on current genome sequence analyses, we found that synonymous codon usage variations in the protein-coding genes of begomoviruses are mainly influenced by mutation bias. Base composition analysis suggested that the codon usage bias of AV1 and BV1 genes is significant and their expressions are high. Fourteen codons were determined as translational optimal ones according to the comparison of codon usage patterns between highly and lowly expressed genes. Interestingly the codon usages between begomoviruses from the Old and the New Worlds are apparently different, which supports the idea that the bipartite begomoviruses of the New World might originate from bipartite ones of the Old World, whereas the latter evolve from the Old World monopartite begomoviruses.
文摘In eukaryotes, a protein motif consisting of WG/GW repeats, also called the Argonaute （AGO） hook, is thought to be essential for binding AGO proteins to fulfill their functions in RNA-mediated gene silencing. Although a number of WG/GW-containing proteins have been computationally identified in Arabidopsis, their roles in plant growth and development are unknown. Here, we show that the Arabidopsis Suppressor of Ty insertion 6-like （SPT6L） gene, which encodes a protein with C-terminal WG/GW repeats, plays critical roles in embryonic development. SPT6L is evolutionarily conserved only in vascular plants, with varying numbers of C-terminal WG/GW repeats, which are plant-species specific. spt61 mutants formed embryos with an aberrant apical-basal axis, showing insufficient development of the basal domain and embryonic lethality. Expression domains of the class-Ill homeodomain-leucine zipper （HD-ZIP III） genes PHABULOSA （PHB） and PHAVOLUTA （PHV） were expanded in the spt61 embryo. In contrast, the PLETHORA1 （PLT1） gene, which acts antagonistically to the HD-ZIP III genes in specification of basal fate, was severely down-regulated in the spt61 mutant. Furthermore, the phb phv double mutations partially rescued aberrant basal development in the spt61 background and restored PLT1 expression. Collectively, our results indicate that SPT6L is essential for specification of the apical-basal axis, partly by controlling the HD-ZIP III genes in embryos.
