Repression of Seed Maturation Genes by a Trihelix Transcriptional Repressor in Arabidopsis Seedlings[W]

The seed maturation program is repressed during germination and seedling development so that embryonic genes are not expressed in vegetative organs. Here, we describe a regulator that represses the expression of embryonic seed maturation genes in vegetative tissues. ASIL1 (for Arabidopsis 6b-interacting protein 1-like 1) was isolated by its interaction with the Arabidopsis thaliana 2S3 promoter. ASIL1 possesses domains conserved in the plant-specific trihelix family of DNA binding proteins and belongs to a subfamily of 6b-interacting protein 1-like factors. The seedlings of asil1 mutants exhibited a global shift in gene expression to a profile resembling late embryogenesis. LEAFY COTYLEDON1 and 2 were markedly derepressed during early germination, as was a large subset of seed maturation genes, such as those encoding seed storage proteins and oleosins, in seedlings of asil1 mutants. Consistent with this, asil1 seedlings accumulated 2S albumin and oil with a fatty acid composition similar to that of seed-derived lipid. Moreover, ASIL1 specifically recognized a GT element that overlaps the G-box and is in close proximity to the RY repeats of the 2S promoters. We suggest that ASIL1 targets GT-box–containing embryonic genes by competing with the binding of transcriptional activators to this promoter region

Analysis of sequence tags in Brassica cotyledons damaged by crucifer flea beetle feeding

The molecular basis of canola (Brassica napus L.) susceptibility to the crucifer flea beetle (FB, Phyllotreta cruciferae Goeze) was investigated by comparing transcript representation in FB-damaged and undamaged cotyledons. The B. napus cotyledon transcriptome increased and diversified substantially after FB feeding damage. Twenty-two genes encoding proteins with unknown function, six encoding proteins involved in signaling, and a gene encoding a B-box zinc finger transcription factor were moderately or strongly changed in representation with FB feeding damage. Zinc finger and calciumdependent genes formed the largest portion of transcription factors and signaling factors with changes in representation. Six genes with unknown function, one transcription factor, and one signaling gene specific to the FB-damaged library were co-represented in a FB-damaged leaf library. Out of 188 transcription factor and signaling gene families screened for \u201cearly\u201d expression changes, 16 showed changes in expression within 8 h. Four of these early factors were zinc finger genes with representation only in the FB-damaged cotyledon. These genes are now available to test their potential at initiating or specifying cotyledon responses to crucifer FB feeding.Les bases mol\ue9culaires de la susceptibilit\ue9 du colza (Brassica napus L.) \ue0 l\u2019altise des crucif\ue8res (Phyllotreta cruciferae Goeze) a \ue9t\ue9 \ue9tudi\ue9e en comparant le transcriptome de cotyl\ue9dons endommag\ue9s ou non par l\u2019altise. Le transcriptome des cotyl\ue9dons du B. napus s\u2019est accru et diversifi\ue9 consid\ue9rablement suite aux dommages caus\ue9s par l\u2019alimentation de l\u2019altise. Vingt-deux g\ue8nes codant pour des prot\ue9ines de fonction inconnue, six codant pour des prot\ue9ines impliqu\ue9es dans la signalisation et un g\ue8ne codant pour un facteur de transcription de type zinc finger \ue0 bo\ueete B ont subi des changements d\u2019expression mod\ue9r\ue9s ou marqu\ue9s en r\ue9ponse aux dommages caus\ue9s par l\u2019altise. Les g\ue8nes \ue0 zinc finger ou r\ue9gul\ue9s par le calcium ont constitu\ue9 la plus grande fraction des facteurs de transcription ou de signalisation dont l\u2019expression \ue9tait alt\ue9r\ue9e. Six g\ue8nes de fonction inconnue, un facteur de transcription et un facteur de signalisation \ue9taient sp\ue9cifiques de la banque produite \ue0 partir de feuilles attaqu\ue9s et co-repr\ue9sent\ue9s au sein de cette banque. Parmi 188 familles de g\ue8nes codant pour des facteurs de transcription ou des prot\ue9ines de signalisation qui ont \ue9t\ue9 examin\ue9s pour des changements d\u2019expression rapides, 16 ont pr\ue9sent\ue9 un changement \ue0 l\u2019int\ue9rieur de huit heures. Quatre de ces facteurs \uab h\ue2tifs \ubb \ue9taient des g\ue8nes \ue0 zinc finger exprim\ue9s uniquement au sein des cotyl\ue9dons endommag\ue9s. Ces g\ue8nes sont maintenant disponibles pour \ue9valuer leur r\uf4le potentiel dans l\u2019initiation ou la d\ue9termination des r\ue9ponses \ue0 l\u2019attaque de l\u2019altise chez le cotyl\ue9don.Peer reviewed: YesNRC publication: Ye