南京農(nóng)業(yè)大學(xué)等處的研究人員從分子水平揭示了引起水稻谷蛋白前體巨增突變性狀的分子機(jī)理，闡述了該基因在谷蛋白合成,、積累中的地位,，利用該突變體及其基因標(biāo)記可為低谷蛋白水稻品種選育提供材料和分子育種的基礎(chǔ),。這一研究成果公布在Plant Journal雜志上。
水稻種子在胚乳中積累大量的儲藏蛋白,，約占籽粒干重的8%%—10%%,，其中谷蛋白占70%%—80%%,，醇溶蛋白占18%%—20%%。提高種子的谷蛋白含量并降低種子的醇溶蛋白含量將會提高稻米的營養(yǎng)價(jià)值,，但是對患有腎臟病和糖尿病的人來說,，谷蛋白的大量吸收將會導(dǎo)致病情的惡化。因此,，深入研究水稻儲藏蛋白合成,、積累的分子機(jī)制對培育滿足不同人群需求的蛋白含量的水稻品種具有重要意義。
在“973”,、“863”以及國家自然科學(xué)基金等支持下,，由萬建民指導(dǎo)課題組通過對一個(gè)自然變異的水稻谷蛋白突變體OsVPE1基因的圖位克隆和功能分析，發(fā)現(xiàn)突變體和野生型間在該基因上只有一個(gè)核苷酸的差異,，導(dǎo)致了突變體中OsVPE1蛋白的269位由Cys突變?yōu)镚ly,，功能互補(bǔ)試驗(yàn)證實(shí)了OsVPE1就是突變基因。該基因的表達(dá)模式和表達(dá)水平在水稻日本晴和W379間雖無顯著差異,，亞細(xì)胞定位結(jié)果顯示突變的蛋白亦分選進(jìn)入液泡中,。但酶活性測定顯示，突變體發(fā)育胚乳中Asn特異剪切活性不到日本晴中的10%%,，Western雜交顯示,，日本晴胚乳中該蛋白能進(jìn)行正確的自我剪切成熟，形成正常的蛋白形式,；而突變體胚乳中的OsVPE1（C269G）大都以前體的形式存在,，其成熟時(shí)剪切發(fā)生了錯(cuò)誤，形成的蛋白分子量小于日本晴中的正常蛋白,，導(dǎo)致其功能喪失,。（生物谷Bioon.com）
生物谷推薦原始出處：
The Plant Journal 19 Jan 2009 DOI：10.1111/j.1365-313X.2009.03801.x
The vacuolar processing enzyme OsVPE1 is required for efficient glutelin processing in rice
Yihua Wang 1 , Susong Zhu 2 , Shijia Liu 1 , Ling Jiang 1 , Liangming Chen 1 , Yulong Ren 1 , Xiaohua Han 1 , Feng Liu 1 , Sulan Ji 1 , Xi Liu 1 and Jianmin Wan 1,2,*
1 National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing 210095, China , and 2 National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China
ABSTRACT
Rice (Oryza sativa L.) accumulates prolamines and glutelins as its major storage proteins. Glutelins are synthesized on rough endoplasmic reticulum as 57-kDa precursors; they are then sorted into protein storage vacuoles where they are processed into acidic and basic subunits. We report a novel rice glutelin mutant, W379, which accumulates higher levels of the 57-kDa glutelin precursor. Genetic analysis revealed that the W379 phenotype is controlled by a single recessive nuclear gene. Using a map-based cloning strategy, we identified this gene, OsVPE1, which is a homolog of the Arabidopsis βVPE gene. OsVPE1 encodes a 497-amino-acid polypeptide. Nucleotide sequence analysis revealed a missense mutation in W379 that changes Cys269 to Gly. Like the wild-type protein, the mutant protein is sorted into vacuoles; however, the enzymatic activity of the mutant OsVPE1 is almost completely eliminated. Further, we show that OsVPE1 is incorrectly cleaved, resulting in a mature protein that is smaller than the wild-type mature protein. Taken together, these results demonstrate that OsVPE1 is a cysteine protease that plays a crucial role in the maturation of rice glutelins. Further, OsVPE1 Cys269 is a key residue for maintaining the Asn-specific cleavage activity of OsVPE1.
