水稻穀粒發育之研究：穀粒蛋白質表現、功能與栽培溫度之 關係﹝3/3﹞

Abstract

Proteins are essential to rice caryopsis development and quality formation. High temperature is an important environmental factor which may decrease grain quality. In the present study rice caryopsis proteins were profiled by two-dimensional polyacrylamide gel electrophoresis, and differentially expressed proteins were analyzed by liquid chromatography/tandem mass spectrometry (LC\MS\MS). Expressions of more than 400 polypeptide spots were monitored during caryopsis development, and more than 70 differentially expressed polypeptides were analyzed by LC\MS\MS. We identified 54 proteins with known functions. Of these, 21 were involved with carbohydrate metabolism, 14 with protein synthesis and sorting, and 9 with stress responses. Waxy (Wx) proteins and glutelins were the most significant spots increased significantly during development. Allergen-like proteins, PPDK and NADH-SDH, also were expressed during development, implying their physiological roles in caryopsis. Expression of large isoforms of Wx proteins was correlated with the amylose content of rice caryopses. One protein with high GC content in its DNA sequence was correlated with the chalky trait of kernels. High temperature (35/30 ℃) decreased expression of Wx proteins, allergen-like proteins and elongation factor 1 β, but increased expression of small heat shock proteins (sHSP), glyceraldehyde-3-phosphate dehydrogenase and prolamin. sHSP was positively correlated with the appearance of chalky kernels. During development, glutelins were phosphorylated and glycosylated, indicating these molecules were post-translationally modified. Possible functions of the expression of candidate proteins on grain quality are discussed.

蛋白質在水稻穎果發育與品質形成過程中扮演重要之角色，高溫為導致水稻 品質降低的主要環境因素之一。本研究利用雙向電泳技術建立水稻穎果蛋白質表 現之基本圖譜，再將其具有表現差異之蛋白質以逢機質譜方式鑑定其種類。本試 驗中可分離至少400個以上的蛋白質，其中70個具表現差異的蛋白質利用 LC\MS\MS的方式進行身分鑑定。並找出57個已知功能的蛋白質。其中包括21個與 碳水化合物生合成或代謝相關的酵素、14個與蛋白質合成或累積相關的酵素以及 9個與逆境反應有關的蛋白質。Waxy與glutelins為最主要隨著發育時期顯著增加 的蛋白質。Allergen-like proteins, PPDK and NADH-SDH等在穎果發育時期具 有重要生理功能的酵素亦被大量表現。其中Waxy基因之數個不同isoforms的表現 量與其質鏈澱粉含量具有相關性。其中一個蛋白質之基因具有高度重複之GC比 例，且其與心腹白之形成有關。高溫(35/30 ℃)會減少Waxy, allergen-like proteins與elongation factor 1β之表現，但會使低分子量之class 1 sHSP大 量表現，G-3-P dehydrogenase, prolamins與sHSP等基因的過量表現與心腹白的 形成具正相關。在穎果發育期間，glutelins有磷酸化與醣化修飾之反應，顯示 其具有轉譯後修飾之作用。穎果發育期間表現之重要蛋白質的功能及其與水稻穀 粒品質形成可能之關聯在文中有進一步之探討。