NtGNL1 Influences Root Hair Growth by Regulating Vesicle Trafficking in Tobacco
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摘要: 极性生长是植物生长发育中的常见现象，但囊泡运输与极性生长的关系还未完全明确。花粉管和根毛是植物细胞极性生长的典型模式。早期研究显示NtGNL1（Nicotiana tabacum GNOM-LIKE 1）通过调节囊泡的后高尔基体转运来影响烟草的花粉管生长。本文以NtGNL1 RNAi转基因植株为材料，研究NtGNL1基因在根毛生长中的作用。结果表明，NtGNL1 RNAi转基因植株的根毛生长明显滞后于野生型，且其根毛出现膨大、弯折、扭曲等形态，与NtGNL1 RNAi转基因植株的花粉管异常形态类似。qRT-PCR检测RNAi转基因株系根毛中PIN1、PIN2、GL2、ROP6、RHD6基因的mRNA表达量，显示PIN2和GL2的表达量显著下调，PIN1、ROP6和RHD6的表达量变化不明显。FM4-64染色表明烟草根表皮细胞和根毛的囊泡分布都受到影响，即NtGNL1基因也影响根毛中的囊泡运输。BFA处理加剧了囊泡的聚集程度，提示根毛尖端还存在其它对BFA敏感并调控囊泡运输的基因。以上证据显示，NtGNL1基因通过囊泡运输途径影响烟草根毛的极性生长，NtGNL1基因的表达下调也影响了PIN2和GL2的表达，从而间接影响根毛的极性生长。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.
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Keywords:
- Nicotiana tabacum /
- NtGNL1 /
- Polar cell growth /
- Root hair /
- Vesicle trafficking /
- RNAi
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