據(jù)外媒報道,，美國研究人員發(fā)現(xiàn),，伽瑪玉米醇溶蛋白（Gamma Zein）會使玉米粒更加堅(jiān)硬，堅(jiān)硬的玉米粒更容易被收割,、存儲和運(yùn)輸,。該發(fā)現(xiàn)可以讓科學(xué)家研發(fā)出更好的雜交玉米，為以玉米為主食的人口提供更多玉米,，也揭示了“優(yōu)質(zhì)蛋白玉米（QPM）”這種品種的玉米既便宜又有營養(yǎng)的原因,。
由于玉米的賴氨酸和色氨酸含量低，并非優(yōu)質(zhì)的蛋白質(zhì)來源,，玉米育種學(xué)家很早就開始注意這一問題,，并致力于玉米蛋白質(zhì)品質(zhì)的改良。經(jīng)過長期的研究實(shí)踐,，改良玉米蛋白質(zhì)品質(zhì)目前主要是通過提高玉米胚乳中谷蛋白含量,，減少醇溶蛋白含量，達(dá)到改善氨基酸組成的目的,，經(jīng)過這一方法改良的玉米被稱為“優(yōu)質(zhì)蛋白玉米”（QPM）,，于上世紀(jì)90年代問世。
在最新一期《美國國家科學(xué)院院刊》（PNAS）上,，羅格斯大學(xué)衛(wèi)克曼微生物研究所主任約基姆·梅辛領(lǐng)導(dǎo)的研究團(tuán)隊(duì)報告了使QPM玉米粒更加堅(jiān)硬的遺傳學(xué)秘密,。
研究人員懷疑兩個負(fù)責(zé)產(chǎn)生伽瑪玉米醇溶蛋白的基因（16號和27號kDa伽瑪玉米醇溶蛋白）會影響QPM玉米粒的堅(jiān)硬度，研究員吳永瑞（音譯）使用一種技術(shù)消除了這兩種基因的表達(dá)后發(fā)現(xiàn),，得到的玉米粒更軟,。
研究人員使用電子顯微術(shù)對初始玉米粒和剔除了基因的玉米粒進(jìn)行了仔細(xì)觀察，結(jié)果發(fā)現(xiàn),，更軟的玉米仁缺乏伽瑪玉米醇溶蛋白,，伽瑪玉米醇溶蛋白同玉米粒中富含淀粉的成分相互連接，同時讓玉米粒保持完整,，也讓玉米粒更加堅(jiān)硬。
約基姆·梅辛表示,，盡管QPM于上世紀(jì)90年代就被研發(fā)出來，科學(xué)家一直不知道可以改變玉米粒的硬度,，新研究表明玉米硬度可以改變,，這將有助于研究人員通過傳統(tǒng)的育種技術(shù)或者基因工程技術(shù)，研發(fā)出更好的玉米雜交品種。同時,，新發(fā)現(xiàn)也將幫助科學(xué)家更好地理解種子和其組成成分是如何進(jìn)化的,。(生物谷Bioon.net)
生物谷推薦原文出處：
PNAS doi: 10.1073/pnas.1004721107
γ-Zeins are essential for endosperm modification in quality protein maize
Yongrui Wu a, David R. Holding b, and Joachim Messing a,1
aWaksman Institute of Microbiology, Rutgers University, Piscataway, NJ 08854; and
bDepartment of Agronomy and Horticulture, Center for Plant Science Innovation, University of Nebraska, Lincoln, NE 68588-0665
Essential amino acids like lysine and tryptophan are deficient in corn meal because of the abundance of zein storage proteins that lack these amino acids. A natural mutant, opaque 2 (o2) causes reduction of zeins, an increase of nonzein proteins, and as a consequence, a doubling of lysine levels. However, o2’s soft inferior kernels precluded its commercial use. Breeders subsequently overcame kernel softness, selecting several quantitative loci (QTLs), called o2 modifiers, without losing the high-lysine trait. These maize lines are known as “quality protein maize” (QPM). One of the QTLs is linked to the 27-kDa γ-zein locus on chromosome 7S. Moreover, QPM lines have 2- to 3-fold higher levels of the 27-kDa γ-zein, but the physiological significance of this increase is not known. Because the 27- and 16-kDa γ-zein genes are highly conserved in DNA sequence, we introduced a dominant RNAi transgene into a QPM line (CM105Mo2) to eliminate expression of them both. Elimination of γ-zeins disrupts endosperm modification by o2 modifiers, indicating their hypostatic action to γ-zeins. Abnormalities in protein body structure and their interaction with starch granules in the F1 with Mo2/+; o2/o2; γRNAi/+ genotype suggests that γ-zeins are essential for restoring protein body density and starch grain interaction in QPM. To eliminate pleiotropic effects caused by o2, the 22-kDa α-zein, γ-zein, and β-zein RNAis were stacked, resulting in protein bodies forming as honeycomb-like structures. We are unique in presenting clear demonstration that γ-zeins play a mechanistic role in QPM, providing a previously unexplored rationale for molecular breeding.
