Abstract:
Polar growth in higher plants is very common, but the relationship between vesicle trafficking and polarity growth is not completely clear. Root hairs and pollen tubes are two typical models of polar cell growth in plants. Previous studies have shown that
NtGNL1 (Nicotiana tabacum GNOM-LIKE 1) plays an important role in tobacco pollen tube elongation by regulating post-Golgi trafficking. Accordingly, we conducted further detailed investigation on
NtGNL1 function in root hair tip growth based on
NtGNL1 RNAi transgenic lines. Results demonstrated that root hair growth was obviously obstructed in
NtGNL1 RNAi transgenic lines in contrast with the control. The
NtGNL1 RNAi root hair phenotypes, such as tip swelling, bending, and curving, were similar to those in pollen tubes of
NtGNL1 RNAi transgenic plants. Using qRT-PCR, the mRNA expressions of the root hair growth polarity genes in
NtGNL1 RNAi transgenic lines were detected, including
PIN1,
PIN2,
GL2, ROP6, and
RHD6. Results showed the expressions of
PIN2 and
GL2 were downregulated significantly, while the expressions of
PIN1,
RHD6, and
ROP6 did not change obviously. Observation of vesicle distribution in the root epidermis cells and root hairs by FM4-64 revealed that the vesicles accumulated inside the cytosol, suggesting that
NtGNL1 affected vesicle trafficking in root hairs. Furthermore, BFA treatment intensified the accumulation, implying that other BFA-sensitive genes were involved in root hair growth. In summary,
NtGNL1 influenced tip growth of root hair via the vesicular trafficking pathway. Also, downregulation of
NtGNL1 reduced the expressions of
PIN2 and
GL2, thus indirectly affecting root hair polarity.