Figure 5.

The knock-out of Arabidopsis ZmUBER1 homolog gene reduces the sensitivity of root growth to chronic ER stress. (a) Location of AtERF9 binding motif on the promoters of UPR genes. The core element is underlined. (b) RT-PCR showing transcript level of AtERF9 in WT and erf9 T-DNA mutant. AtACT7 was used as a loading control. (c) qRT-PCR showing the relative expression levels of UPR genes normalized to the mock control (DMSO-only) at 24 h of Tm treatment. Means ± SEM; three biological replicates. *P < 0.05, Student’s t-test. (d) Relative growth rate of the primary root of WT, erf9 and bzip28-2 bzip60-1 in chronic ER stress. bzip28-2 bzip60-1, which is known to be lethal in chronic ER stress (Deng et al., 2013), was used as a negative control in the experiment. Seeds were directly germinated and grown on the growth media in split plates of which one half contained Tm (25 ng/mL) while the other half contained only DMSO (corresponding mock control). The relative growth rate was measured seven days after growth. Means ± SEM; five biological replicates (n = 4-5 per replicate, with five seedlings for replicate). *P < 0.05, **P < 0.001 (Student’s t-test). Representative pictures are shown. Scale bar (black) = 1.3 cm.