Unknown,Transcriptomics,Genomics,Proteomics

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Responses of tobacco BY-2 cells to boron deprivation

ABSTRACT: Boron (B) is an essential micronutrient for vascular plants. Boron works to build the cell wall structure by forming borate ester cross-links with pectin, and the deficiency of this element brings about oxidative damage and cell death. However, the process via which B deficiency leads to such serious damage has not been well understood. We investigated the temporal changes in metabolism of B-deprived cultured tobacco (Nicotiana tabacum) BY-2 cells by analyzing their gene expression using cDNA microarray. Three-day-old cells were deprived of B by washing with and transferred to B-free growth media ("-B" cells). Cells similarly treated with standard growth media were employed as a control for the effects of mechanical stress ("+B cells"). Cells were sampled at 1, 3, 6, 12 and 36 h after transfer to the B-free or standard media. Cells without washing treatment were also included in the analysis ("before-treatment cells"). Two independent sets of samples were analyzed (replicate 1 and 2).

ORGANISM(S): Nicotiana tabacum

SUBMITTER: Masaru Kobayashi

PROVIDER: E-GEOD-37649 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Guanosine 3 ,5 -bispyrophosphate (ppGpp), also known as ‘‘magic spot,’’ has been shown to bind prokaryotic RNA polymerase to down-regulate ribosome production and increase transcription of amino acid biosynthesis genes during the stringent response to amino acid starvation. Because many environmental growth perturbations cause ppGpp to accumulate, we hypothesize ppGpp to have an overarching role in regulating the genetic program that coordinates transitions between logarithmic growth (feast) and growth arrest (famine). We used the classic glucose-lactose diauxie as an experimental system to investigate the temporal changes in transcription that accompany growth arrest and recovery in wildtype Escherichia coli and in mutants that lack RelA (ppGpp synthetase) and other global regulators, i.e., RpoS and Crp. When cultured on a mixture of glucose and lactose, E. coli grows preferentially on glucose until it is exhausted, resulting in growth arrest while the cells adjust to growth on lactose, i.e., diauxie. Diauxie was delayed in the relA mutant and was accompanied by a 15% decrease in the number of carbon sources used and a 3-fold overall decrease in the induction of RpoS and Crp regulon genes. Thus the data significantly expand the previously known role of ppGpp and support a model wherein the ppGpp-dependent redistribution of RNA polymerase across the genome is the driving force behind control of the stringent response, general stress response, and starvation-induced carbon scavenging. Our conceptual model of diauxie describes these global control circuits as dynamic, interconnected, and dependent upon ppGpp for the efficient temporal coordination of gene expression that programs the cell for transitions between feast and famine. E. coli MG1655 and isogenic mutants were cultured in a 2 l Biostat B fermentor (B. Braun Biotech International) containing 1 liter of Morpholinepropanesulfonic acid (MOPS) minimal medium with 0.5 g/l of glucose and 1.5 g/l of lactose. The temperature was maintained at 37 ºC and pH was kept constant at 7.2 by the addition of 2 M NaOH. The dissolved oxygen level was maintained above 20% of saturation by adjusting the agitation speeds in the range of 270-500 rpm with fixed 1 l/min air flow.

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Responses of tobacco BY-2 cells to boron deprivation

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