hypocotyl - Arabidopsis Col0 Seedlings were cultured on a Murashige and Skoog medium as described by Estelle and Somerville (1987) but without sucrose. Seeds were arrayed individually on a Nylon filter (BioTechnoFix) on 9cm petridishes and incubated for 72h at 4degreeC, followed by 4h at 20degreeC, under white light (100umol/m2s). Plates were wrapped in 3 layers of aluminum foil and incubated at 20degreeC for the indicated time periods. Upon harvest, 3hypocotyls were dissected out under green light (approximately 30 hypocotyls per experiment), the dissection took approximately 10 min per time point. 16 harvests were pooled, in total 475 hypocotyls, for each time point. RNA was extracted using the trizol reagent (Invitrogen).
Extracted molecule
total RNA
Extraction protocol
CesA_52h:3.45ug.
Label
Cy5
Label protocol
labelling Cy3 and Cy5 indirect, amplification=yes, DNA 5 ug. Labelling protocol: 5 µg of aRNA (8µl) mixed with 2 µl of random nonamers 1µg/µl and 0.5 µl of RNAse Out 40 U/µl, denatured 10 min at 70 °C and chilled on ice. The followig components were added to the sample 4 µl of first strand buffer 5 X, 1 µl of 10 mM dNTP/2mM dCTP, 2 µl of 0.1 M DTT, 1.5 µl of Cy3-dCTP or Cy5-dCTP (Amersham Pharmacia Biotech, 25nmol tube, PA5502), 1 µl of SuperScript II RT 200U/µl. Then it was incubated at 42°C for 2.5 hours and chilled on ice. The sample was denaturated by adding 2 µl of NaOH 2.5M and incubated at 37 °C for exactly 15 min, then was added 10 µl of 2M MOPS and put on ice. The dyes were purified with the QIAquick PCR Purification Kit (QIAGEN).
hypocotyl - Arabidopsis Col0 Seedlings were cultured on a Murashige and Skoog medium as described by Estelle and Somerville (1987) but without sucrose. Seeds were arrayed individually on a Nylon filter (BioTechnoFix) on 9cm petridishes and incubated for 72h at 4degreeC, followed by 4h at 20degreeC, under white light (100umol/m2s). Plates were wrapped in 3 layers of aluminum foil and incubated at 20degreeC for the indicated time periods. Upon harvest, 3hypocotyls were dissected out under green light (approximately 30 hypocotyls per experiment), the dissection took approximately 10 min per time point. 16 harvests were pooled, in total 475 hypocotyls, for each time point. RNA was extracted using the trizol reagent (Invitrogen).
Extracted molecule
total RNA
Extraction protocol
CesA_55h:2.61ug.
Label
Cy3
Label protocol
labelling Cy3 and Cy5 indirect, amplification=yes, DNA 5 ug. Labelling protocol: 5 µg of aRNA (8µl) mixed with 2 µl of random nonamers 1µg/µl and 0.5 µl of RNAse Out 40 U/µl, denatured 10 min at 70 °C and chilled on ice. The followig components were added to the sample 4 µl of first strand buffer 5 X, 1 µl of 10 mM dNTP/2mM dCTP, 2 µl of 0.1 M DTT, 1.5 µl of Cy3-dCTP or Cy5-dCTP (Amersham Pharmacia Biotech, 25nmol tube, PA5502), 1 µl of SuperScript II RT 200U/µl. Then it was incubated at 42°C for 2.5 hours and chilled on ice. The sample was denaturated by adding 2 µl of NaOH 2.5M and incubated at 37 °C for exactly 15 min, then was added 10 µl of 2M MOPS and put on ice. The dyes were purified with the QIAquick PCR Purification Kit (QIAGEN).
Hybridization protocol
52h Cy5 / 55h Cy3 : 40pmol.
Scan protocol
GenePix Pro 3.0, Cy3:pmt voltage 532nm,650V,laser power 100%, Cy5:635nm,pmt voltage 650V,laser power 100%
Description
1. Study the molecular basis of the growth acceleration observed in hypocotyl cells. We previously have observed that cell elongation takes place in two distinct phases (Refregier et al., 2004). A slow growth phase during which a thick polylamellated wall is deposited and a rapid growth phase during which cell wall polymers are extensively remodelled. In dark-grown hypocotyls the slow growth phase takes place during the first 48h after seed-imbibition synchronously in all cells. At 48h after imbibition, cells at the basis of the hypocotyl undergo a growth acceleration, this acceleration follows an acropetal gradient along the hypocotyl. In this experiment, we investigated the changes in transcript abundance that accompany this sudden increase in growth rate. 2. Study the feed-back mechanisms involved in the coordination between cellulose synthesis and the cell elongation. The inhibition of cellulose using chemical inhibitors also inhibits cell elongation. In the same study (Refregier et al., 2004), we have observed that the effect of the cellulose synthesis inhibitor isoxaben on cell elongation is different dependent on the growth stage. When applied during the slow growth phase, cells continue to elongate slowly and do not show the growth acceleration at 48h after imbibition. Surprisingly, when applied after the growth acceleration, isoxaben does not inhibit subsequent growth. In this study we compared the effects of isoxaben on the transcript profiles before and after the growth acceleration. This should inform us about the response of the hypocotyl cells to the inhibition of cellulose and should provide insights into the molecular events that underly the observed coupling between cellulose synthesis and cell elongation.
Data processing
The raw data comprised the logarithm of median feature pixel intensity at wavelength 635 nm (red) and 532 nm (green). No background was subtracted. An array-by-array normalization was performed to remove systematic biases. First, we excluded spots that were considered badly formed features by the experimenter (Flags=-100). Then we performed a global intensity-dependent normalization using the loess procedure (see Yang et al., 2002) to correct the dye bias. Finally, on each block, the log-ratio median is subtracted from each value of the log-ratio of the block to correct a print-tip effect on each metablock.
