Ment after incubation with A-ODNs. Preliminary experiments revealed that the uptake of Alexa Fluor 488 occurs on a much longer time frame than that of FM4-64; thus, we first incubated pollen tubes with FLODNs for 223 h and then added FM4-64 to visualize endocytosis. Endocytosis occurred primarily in the apex and the shank of the pollen tube. However, the Alex Fluor 488 signal (green) appeared in all parts of pollen tubes, especially at the tip (Fig. 1B.b). The two regions only partially overlapped and displayed distinct distribution patterns, with more green at the apex (Fig. 1B.d) and more red signals along the shank (Fig. 1B.f,g), indicating that the uptake of A-ODN occurred actively at the apex. These results indicate that the A-ODNs likely passed into the pollen tube via some pathway(s) only at the apex.A-ODN Specifically Down-regulate NtGNL1 ExpressionTo evaluate the possibility of off-target and toxic effects of the A-ODN on pollen tube growth, we designed several A-ODNs with differing sequences, based on the NtGNL1 mRNA sequence (Table 1). We also applied sense ODN and scrambled ODN containing the same nucleotides in a different (nonsense) orderdoi:10.1371/journal.pone.0059112.tAntisense ODN Inhibition in Pollen TubesFigure 3. Inhibition effects of A-ODN on pollen germination and pollen tube growth. A, Up to 80 of the control, wild-type pollen germinated after 4 h of culturing, whereas less than 60 of the pollen in antisense ODN media germinated (n = 300). Double asterisks indicate P,0.01 between control (ck) and treated sample [SPSS (16.0) Independent-Sample T Test]. Error bars in the columns represent SD. B, A bright field image showing pollen grains germinated in control (CK) after 4 h. C, Approximately half of the pollen grains germinated in A-ODN (20 mM) medium at the same time. Bar = 50 mm. D, E, Pollen tube length comparison between control and A-ODN (5 mM) treated pollen tubes. Pollen tubes in control media (D) were clearly longer than those grown in A-ODN medium (E). Bar = 100 mm. E , Phenotypes of A-ODN (20 mM) treated pollen tubes: bulging (F), curved (G), zigzag (H), bending (I). doi:10.1371/journal.pone.0059112.g(Table 1). These served as controls to observe the pollen tube phenotype. Among these A-ODNs, ON4 and ON6 showed similar effects on pollen tube growth (Fig. 2A). This get SPDP phenotype was similar to that observed in NtGNL1 RNAi plants, suggesting the phenotypes involved suppression of NtGNL1 expression. Other ODNs used in these experiments, including the sense ODN and scrambled ODN, showed no significant influence on pollen tube growth (Fig. 2B). To assess NtGNL1 mRNA expression levels, we 
extracted RNA from both control and A-ODN-treated pollen tubes, and the results confirmed that NtGNL1 mRNA expression levels were reduced by the specific A-ODN (Fig. 2C). We primarily used ON4 in the following experiments and selected scrambled (random) MedChemExpress CASIN sequences of ON4 as a control. To test the possible toxic effects of the sequences, we compared the viability of sense- vs. ON4-treated pollen tubes (Fig. S2). No significant difference was observed in terms of the percentage of viable pollen tubes from each treatment (Fig. 2D). All treated pollen tubes showed similar viability, suggesting against the possibility of toxic effects due to A-ODN sequences.Inhibition of NtGNL1 Expression Disturbs Pollen Tube Elongation and OrientationThe germination frequency of ODN-treated pollen was significantly lower than that in the control (Fig.Ment after incubation with A-ODNs. Preliminary experiments revealed that the uptake of Alexa Fluor 488 occurs on a much longer time frame than that of FM4-64; thus, we first incubated pollen tubes with FLODNs for 223 h and then added FM4-64 to visualize endocytosis. Endocytosis occurred primarily in the apex and the shank of the pollen tube. However, the Alex Fluor 488 signal (green) appeared in all parts of pollen tubes, especially at the tip (Fig. 1B.b). The two regions only partially overlapped and displayed distinct distribution patterns, with more green at the apex (Fig. 1B.d) and more red signals along the shank (Fig. 1B.f,g), indicating that the uptake of A-ODN occurred actively at the apex. These results indicate that the A-ODNs likely passed into the pollen tube via some pathway(s) only at the apex.A-ODN Specifically Down-regulate NtGNL1 ExpressionTo evaluate the possibility of off-target and toxic effects of the A-ODN on pollen tube growth, we designed several A-ODNs with differing sequences, based on the NtGNL1 mRNA sequence (Table 1). We also applied sense ODN and scrambled ODN containing the same nucleotides in a different (nonsense) orderdoi:10.1371/journal.pone.0059112.tAntisense ODN Inhibition in Pollen TubesFigure 3. Inhibition effects of A-ODN on pollen germination and pollen tube growth. A, Up to 80 of the control, wild-type pollen germinated after 4 h of culturing, whereas less than 60 of the pollen in antisense ODN media germinated (n = 300). Double asterisks indicate P,0.01 between control (ck) and treated sample [SPSS (16.0) Independent-Sample T Test]. Error bars in the columns represent SD. B, A bright field image showing pollen grains germinated in control (CK) after 4 h. C, Approximately half of the pollen grains germinated in A-ODN (20 mM) medium at the same time. Bar = 50 mm. D, E, Pollen tube length comparison between control and A-ODN (5 mM) treated pollen tubes. Pollen tubes in control media (D) were clearly longer than those grown in A-ODN medium (E). Bar = 100 mm. E , Phenotypes of A-ODN (20 mM) treated pollen tubes: bulging (F), curved (G), zigzag (H), bending (I). doi:10.1371/journal.pone.0059112.g(Table 1). These served as controls to observe the pollen tube phenotype. Among these A-ODNs, ON4 and ON6 showed similar effects on pollen tube growth (Fig. 2A). This phenotype was similar to that observed in NtGNL1 RNAi plants, suggesting the phenotypes involved suppression of NtGNL1 expression. Other ODNs used in these experiments, including the sense ODN and scrambled ODN, showed no significant influence on pollen tube growth (Fig. 2B). To assess NtGNL1 mRNA expression levels, we extracted RNA from both control and A-ODN-treated pollen tubes, and the results confirmed that NtGNL1 mRNA expression levels were reduced by the specific A-ODN (Fig. 2C). We primarily used ON4 in the following experiments and selected scrambled (random) sequences of ON4 as a control. To test the possible toxic effects of the sequences, we compared the viability of sense- vs. ON4-treated pollen tubes (Fig. S2). No significant difference was observed in terms of the 
percentage of viable pollen tubes from each treatment (Fig. 2D). All treated pollen tubes showed similar viability, suggesting against the possibility of toxic effects due to A-ODN sequences.Inhibition of NtGNL1 Expression Disturbs Pollen Tube Elongation and OrientationThe germination frequency of ODN-treated pollen was significantly lower than that in the control (Fig.
