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Flowering of bamboo albino somatic embryos (3-7-2007) |
 Two reports on flower proliferation of albino somatic embryos and derived plantlets of bamboo Dendrocalamus from Wei-chin Chang's Lab (CS Lin et al., New Forest. in press; CS Lin et al., In Vitro/Plant. 42: 336-340 2006) provided methods for making flowers in test tubes. Their protocols described can be used to produce large numbers of mutant inflorescence within a relatively short period. And those flowering processes are being used for studies on relations among juvenility, flowering, and programmed death. |
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| Trans-acting siRNAs: are there more to be found? (3-14-2007) |
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| Small RNAs play pivotal roles in regulating gene expression in higher eukaryotes. Among them, trans-acting siRNAs (ta-siRNAs) are a new class of small RNAs that regulate plant development. With the recent advances in large-scale sequencing of small RNAs via MPSS or 454 sequencing technologies, Shu-Hsing Wu's group was interested in the development of computational algorithms that could be broadly applied to predict TASgenes by data mining any given large-scale small RNA sequencing data with no restriction in prior knowledge of miRNA/siRNA target sites and of non-restricted organism origin. By integrating statistical evaluation, an algorithm for detecting TAS genes was developed and used for the search of new TAS genes (HM Chen, YH Li, SH Wu: Bioinformatic prediction and experimental validation of a microRNA-directed tandem trans-acting siRNA cascade in Arabidopsis PNAS 104: 3318-3323, 2007). The biogenesis of ta-siRNAs from two TAS/PPR genes and the trans-acting activity of one of the ta-siRNAs were experimentally confirmed. The results also indicate the existence of a small RNA regulatory cascade initiated by miR173-directed cleavage and followed by the consecutive production of ta-siRNAs from two TAS genes. |
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| Ectopic expression of ABA2/GIN1 in Arabidopsis promotes seed dormancy and stress tolerance (1-25-2007) |
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| Abscisic acid (ABA) is a major phytohormone that plays critical roles in seed development, maturation, and dormancy, and is also involved in stomatal closure, flowering time, and stress resistance. Genes involved in ABA biosynthesis have been studied in the past decade. The gene ABA2 encodes a short-chain dehydrogenase/reductase1 (SDR1) that catalyzes the multiple-step conversion of xanthoxin into abscisic aldehyde in the cytosol. As ABA2 has not been considered to be a rate-limiting enzyme in ABA biosynthesis, effect of ABA2 overexpression in transgenic plants on ABA levels remains unknown. Wan-Hsing Cheng's group recently demonstrated that transgenic Arabidopsis overexpressing ABA2 with elevated ABA levels promote delay of seed germination and tolerance to salt. Study with ABA2 promoter activity through analysis of ABA2::GUS transgenic plants revealed that ABA2 is a late expression gene. They proposed ABA2 might have a fine-tuning function in mediating ABA biosynthesis through primary metabolic change in response to long-term stress conditions (Plant Physiol. in press). Click here for the preview text on Plant Physiol Online. |
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