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Abstract: Fructose 1,6-biphosphate aldolase (FBA) is a key enzyme in plants, which is involved not only in glycolysis and gluconeogenesis in the cytoplasm, but also in the Calvin cycle in plastids. Research on FBAs in various organisms has been reported, but there is none on FBAs in Arabidopsis at the molecular level. In the current study, eight FBA family genes (AtFBA1–8) were identified and analyzed in Arabidopsis thaliana. These genes have a highly conserved aldolase-type TIM barrel domain and a C-terminal peptide, but variable N-terminal peptides. Based on the phylogenetic analysis of FBA protein sequences from Arabidopsis and other plant species, AtFBA family was classified into two subfamilies, including three members (AtFBA1–3) with high similarities to FBAs occurring at plastid, and five (AtFBA4–8) with high similarities to FBAs localized in the cytoplasm. By confocal microscopy analysis with GFP fusion protein, AtFBA3 and AtFBA4 as well as AtFBA6 were observed to be localized in the plastid and cytoplasm, respectively. At least two duplicated gene pairs of AtFBA1 and AtFBA2, as well as AtFBA4 and AtFBA8 were found. Transcript level analysis of AtFBA genes in various tissues revealed the unique and overlapping expression patterns of plastid and cytosol AtFBA genes, suggesting that these genes may function at different stages of plant growth and development. Interestingly, AtFBA1, AtFBA2, AtFBA5 and AtFBA7 showed undetectable expression in roots. The expression patterns of AtFBA genes under different stress conditions suggested that all the members showed different expression patterns in response to stresses, including ABA, NaCl, Cd, abnormal temperature and drought, and, except for AtFBA3, most of the AtFBA genes were significantly responsive to drought stress in roots. Moreover, AtFBA1, AtFBA2, AtFBA5, AtFBA7 and AtFBA8 were induced by at least one of three sugars (sucrose, glucose and fructose) after 24h of treatment. Further functional analyses indicated important clues of AtFBA2, AtFBA6 and AtFBA8 in plant growth, stress responses and development, respectively. Thus these results provide additional knowledge on AtFBA families and their roles. [Copyright &y& Elsevier]

Abstract: Being poikilothermic and sessile organisms, plants have to respond quickly to changing environmental cues, and a higher order of gene regulation is required. The significance of nucleocytoplasmic transport via importinα and importinβ (α/β) has been exhibited in a wide spectrum of biological processes. However, most of these receptors have not been characterized as to which cellular or development processes are required and how their expression is regulated by environmental stimuli. Here we pursued a phylogenetic analysis and investigated the expression patterns of all 8 IMPαs and 18 IMPβs in Arabidopsis. The IMPα isoforms could be tracked back to a common ancestor, while the IMPβs derived from different ones. The majority of transport receptor genes were constitutively expressed. Intriguingly, AtIMPα5, 7, 8 and AtIMPβ5 were specifically expressed in different tissues. AtIMPβ3 was the sole receptor that was obviously modulated by exogenous phytohormones, whereas three IMPαs and five IMPβs exhibited responses to environmental stimuli. Furthermore, our RT-PCR data provided direct evidence that AtIMPα5, 8 and AtIMPβ5 are not pseudogenes and we also corrected the open reading frame annotation of AtIMPα8. These genome-wide profiling results not only widen our understanding of these transport receptors, but also provide strong evidence supporting the role of transport receptors in multiple signaling pathways and give us an insight into the further analysis of nucleocytoplasmic trafficking in Arabidopsis. [Copyright &y& Elsevier]