Project description:Photoperiod is a circannual signal measured by biological systems to align growth and reproduction with the seasons. To understand the effect of photoperiod of gene expression in Arabidopsis thaliana in the absence of exogenous sugar under constant light intensity, we performed time course mRNA-seq analysis on 13-day old seedlings across three photoperiods with triplicates to identify photoperiod-regulated genes.
Project description:Analysis of gene expression in Arabidopsis thaliana leaf, stem and flower tissues. Columbia (Col-0) Arabidopsis thaliana plants were grown at a density of 4 plants per 5 inch square pot either in a growth chamber or a green house set to 25*C by day, 20*C by night. Days were set to a 16hr photoperiod with 125 micro mol m-2s-1 fluorescent irradiation. Expanding leaves were harvested 15 days post germination in the middle of the photoperiod (3 replicates). Expanding upper 2" of the stem with siliques and pedicels removed were harvested 29 days post germination in the middle of the photoperiod (4 replicates). Developed flowers and unopened buds were harvested 29 days post germination in the middle of the photoperiod (4 replicates). RNA and Microarray Methods: Total RNA was extracted from the plants using the Trizol method (Invitrogen, Ramonell et al. (2002) Mol. Plant Pathol. 3: 301) and purified with a silica membrane column (Qiagen, RNeasy). Twenty micrograms biotinylated complementary RNA (cRNA) was prepared as described (Hernan et al. (2003) Cancer Res. 63, 140) from the purified total RNA. The resulting cRNA was used to hybridize ATH1 Arabidopsis GeneChips (Affymetrix) using the manufacturer's protocols. The array images were analyzed with the Affymetrix Microarray Suite 5.0 software with the target intensity set to 500. Normalized signal intensities were generated by multiplying signal intensities by ratio figure which set GapC (ID_REF = 258588_s_at) to 8500. Keywords: other
Project description:Plants are exposed to regular diurnal rhythms of light and dark. Changes in the photoperiod by the prolongation of the light period cause photoperiod stress in short day-adapted Arabidopsis thaliana. Here we report on the transcriptional response to photoperiod stress of wild-type A. thaliana and photoperiod stress-sensitive cytokinin signaling and clock mutants. Transcriptomic changes induced by photoperiod stress included numerous changes in reactive oxygen species (ROS)-related transcripts and showed a strong overlap with alterations occurring in response to ozone stress and pathogen attack, which have in common the induction of an apoplastic oxidative burst. A core set of photoperiod stress-responsive genes has been identified, including salicylic acid (SA)-biosynthesis and -signaling genes. Genetic analysis revealed a central role for NPR1 in the photoperiod stress response as npr1-1 mutants were stress-insensitive. Photoperiod stress treatment led to a strong increase in camalexin levels which is also observed in response to pathogen infections. Photoperiod stress induced the resistance of Arabidopsis plants to a subsequent infection by Pseudomonas syringae pv. tomato DC3000 indicating priming of the defence response. Together, photoperiod stress causes transcriptional reprogramming resembling plant pathogen defence responses and induces systemic acquired resistance in the absence of a pathogen.
Project description:Plants in temperate regions have evolved mechanisms to survive sudden temperature drops. Previous reports have indicated that the cold acclimation mechanism is light-dependent and does not fully operate under a low light intensity. In these studies, plants were grown under a long-day photoperiod and were more sensitive to freezing stress. However, winter annuals like Arabidopsis thaliana Col-0 germinate in the fall, overwinter as rosettes, and therefore must acclimate under short photoperiods and low irradiance. The role of light intensity was analysed in plants grown under a short-day photoperiod at the growth stage 1.14. Plants were acclimated at 4 °C for seven days under 100 and 20 μmol m-2s-1 PPFD for control and limited-light conditions, respectively. All cold acclimated plants accumulated molecular markers reportedly associated with acquired freezing tolerance, including proline, sucrose, CBFs, and COR gene protein products dehydrins and low-temperature-responsive proteins LTIs. Observed changes indicated that low PPFD did not inhibit the cold acclimation process, and the freezing stress experiment confirmed similar survival rates. The molecular analysis found distinct PPFD-specific adaptation mechanisms that were manifested in contrasting content of anthocyanins, cytokinin conjugates, abundances of proteins forming photosystems, and enzymes of protein, energy, and ROS metabolism pathways. Finally, this study led to the identification of putative proteins and metabolite markers correlating with susceptibility to freezing stress of non-acclimated plants grown under low PPFD. Our data show that Arabidopsis plants grown under short-day photoperiod can be fully cold-acclimated under limited light conditions, employing standard and PPFD-specific pathways.