Transcript levels of selected isogroups across a senescence leaf time course. Expression levels in WT and GPC-RNAi plants were determined using qRT-PCR at four points across a senescing leaf time course (H = heading, D = days after anthesis). Transcript levels are presented as normalized linearized values using the 2-ΔΔC tmethod , where Ct is the threshold cycle. Values are corrected using the same calibrator across genes and therefore the transcript level scale is comparable between isogroups. Each data point is an average based on ten plants (± SEM). * P≤0.05, ** P≤0.01.