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. 2017 Mar 7;8:256. doi: 10.3389/fpls.2017.00256

Figure 1.

Figure 1

Auxin responses to outside stimuli at DR5-VENUS root tip. (A) 500 nM NAA treated 3-days old DR5-VENUS rice seedlings for 3 days; images were taken at root tip and root hair zone. NAA raises auxin response at the epidermal (arrowheads), and columella cells (arrows). Scale bar: 50 μm. (B) Quantification of relative mRNA levels of auxin transporter genes after NAA treatment. Auxin responsive gene OsGH3.2 is used as positive control. All the data were expressed as mean ± SEM from three biological and three technical repeats. Statistically significant differences (Student's t-test, P < 0.01) between mock control (CK) and NAA treatment are indicated by two asterisks. Expression levels of all auxin transporters were increased after NAA treatment, including OsAUX1. (C) 100 nM NPA inhibition effect on DR5-VENUS rice primary root for 1 day. Auxin profile becomes much broader after NPA treatment and expands into cortex layers inside meristem. Scale bar: 50 μm. (D) Quantification of relative mRNA levels of auxin transporter genes after NPA treatment. OsGH3.2 is used as reference gene induced by auxin. All the data were expressed as mean ± SEM from three biological and three technical repeats. Statistically significant differences (Student's t-test, P < 0.05) are indicated by one asterisk. NPA has no effect on OsPIN1 genes except for OsPIN1c slightly induced by NPA. (E) Root gravitropism assay of rice wild type 9522 cultivar (CK). Root tip angle reaches up to 45 degrees at about 2.5 h after rotation in Rice. Root tip angles were calculated using image J software. All the data were expressed as mean ±SEM (Root Number = 8). (F) DR5 signal redistribution at epidermis cell layer and root cap region under a gravity stimulus of 2.5 h. “U” represents the epidermis layer at upper side. DR5-VENUS signals at epidermis upper side are weaker under gravistimulation. Scale bar: 25 μm. White dotted lines highlight the lower region of lateral root cap where auxin accumulates. (G) DR5-VENUS signals at the root tip after 500 nM Trans-zeatin (cytokinin) application on 3-days old rice seedlings. Scale bar: 50 μm. Trans-zeatin induces relocation of auxin response from root cap to epidermis and cell initials inside meristem. (H) Quantification of relative mRNA levels of auxin transporter genes after cytokinin treatment. Type-A cytokinin responsive genes OsRR3 and OsRR6 are selected as positive control genes. All the data were expressed as mean ± SEM from three biological and three technical repeats. Statistically significant differences (Student's t-test, **P < 0.01; *P < 0.05) are marked out. OsPIN1c and OsPIN1d are significantly reduced while OsPIN1a slightly increased under CK treatment. (A,C,F,G) Red channel, propidium iodide; Green channel, VENUS.