Arabidopsis HIT1, a Putative Homolog of Yeast Tethering Protein Vps53p, is Required for Pollen Tube Elongation

囊泡繫鏈同源蛋白質HIT1為阿拉伯芥花粉管伸長之必要因子

王亮晴(Lian-Chin Wang) ； 葉靖輝(Ching-Hui Yeh) ； Ronald J. Sayler ； 李雅韻(Ya-Yun Lee) ； 陸重安(Chung-An Lu) ； 吳少傑(Shaw-Jye Wu)

《Botanical Studies》 49卷1期 (2008/01) Pp. 25-32

摘要

阿拉伯芥HIT1基因所編碼之蛋白質，與酵母菌囊泡繫鏈蛋白質Vps53p有同源性。由乙基甲基磺酸酯(Ethyl methane sulfonate)所造成之點突變對偶基因hit1-1，可以以同型合子(homozygous)的方式存在。帶有T-DNA插入之對偶基因hit1-2及hit1-3，則只能以半合子(hemizygous)的方式存在。將野生種與突變種進行正反交實驗，結果顯示hit1-2及hit1-3只能以半合子的方式存在，起因於雄配子體的缺陷。進一步以HIT1啟動子嵌合GUS報導基因做實驗，結果顯示在生殖器官的部份，HIT1基因的表現主要是在成熟的花粉粒及延伸的花粉管。以離體方式量測花粉管的發育，顯示來自於hit1-1/hit1-1同型合子植株之花粉粒，可以長出花粉管，但長度較野生種之花粉管為短。來自於HIT1/hit1-2或HIT1/hit1-3異型合子植株之花粉粒，約半數可長出長度近似野生種之花粉管，其餘之花粉粒則無法發育出花粉管。由上述之結果推知，HIT1可能參與了某花粉管尖端生長(tip growth)所必須之囊泡運送，該運送機轉若因HIT1的損傷而失去作用，將造成雄配子體之不孕。此外，hit1-1應為部分功能喪失之對偶基因，而hit1-2及hit1-3則為無工能之對偶基因。

關鍵字

阿拉伯芥 ； 花粉管 ； 尖端生長 ； 囊泡繫鏈因子

並列摘要

The Arabidopsis HIT1 gene encodes a protein that is homologous to the yeast tethering factor Vps53p, which is involved in retrograde vesicle trafficking from the endosome to the trans-Golgi network. Although the ethyl methanesulfonate mutagenized hit1-1 allele can be maintained homozygously, T-DNA insertional hit1-2 and hit1-3 mutants can only be isolated as hemizygous lines. No heterozygous progeny were produced in outcrosses to wild-type plants using pollen from either hit1-2 or hit1-3 heterozygotes. The reciprocal cross using pollen from wild-type plants on either hit1-2 or hit1-3 mutants produced heterozygous and wild-type progeny. In reproductive tissues, HIT1 promoter-driven GUS activity was detected only in mature pollen and elongated pollen tubes. In vitro pollen germination further showed that only half the pollen grains from hit1-2 and hit1-3 heterozygote plants produced normal pollen tubes. In contrast, the pollen tube length of pollen grains from the hit1-1 mutant was reduced compared to that of the wild type. These results suggest that HIT1 may govern a vesicle trafficking event that is required for pollen tube tip growth during male gametogenesis and that disruption of HIT1 results in male specific transmission defect. Moreover, while the hit1-1 mutant is partially functional leading to reduced pollen tube length, hit1-2 and hit1-3 are total-loss-of-function alleles.

並列關鍵字

Arabidopsis thaliana ； Pollen tube ； Tip growth ； Vesicle tethering factor ； Yeast Vps53p protein