2008-08-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/697752摘要：藉由非致命的熱休克(HS)反應的前處理，可引起熱休克蛋白質(HSPs)的生成及累積，已被廣泛地報告與生物體獲得耐熱性有關。不過，我們發現大豆幼苗在外加鈣離子螯合劑EGTA處理下，在HS期間可引起細胞內容物的滲漏增加，剝奪植物獲得耐熱性的能力。透過二價的陽離子，特別是鈣離子的&#21442;與可恢復此能力。基於EGTA處理並不影響HSP累積和其正常生理的功能，証實除了HSPs之外，細胞間因HS誘導而釋出並且可再被吸收的鈣離子與植物獲得耐熱性有正相關。細胞壁間PME (pectin methylesterase) 及PG (polygalacturonase) 酵素的活動&#21442;與了此項功能，用以調整及重新規劃細胞壁結構、影&#21709;細胞壁的質地、防止細胞的分離，以便維持細胞膜的正常通透。並且在HSPs的協同下&#21442;與植物耐熱性了的獲得。<br> Abstract: Heat shock proteins (HSPs) induced by non-lethal heat shock (HS) have been widely reported as molecular chaperones in conferring thermotolerance. However, we found that acquired thermotolerance of 2-d etiolated soybean (Glycine max) seedlings reduced by an exogenously supplied extracellular Ca2+ chelator, ethylene glycol-bis(2-aminoethyl ether)-N,N,N`,N`-tetraacetic acid (EGTA), which caused increased cellular leakage during HS. Thermotolerance was restored by adding divalent cations, specifically Ca2+, during EGTA incubation. In addition to HSPs, apoplastic Ca2+, which was released by HS and could be reabsorbed to counteract an otherwise lethal HS, was involved in the development of heat tolerance, because EGTA did not affect HSP accumulation and physiological functions. The activity of pectin methylesterase (PME), a cell wall remodeling enzyme, was enhanced during HS and reduced by EGTA but restored with Ca2+ suggests that PME activation in response to HS. The model structure of an “egg-box”, a major apoplastic Ca2+ reservoir containing a Ca2+-pectate to confer the texture and rigidity of the cell wall, was destructured on challenge with HS and EGTA, but recovery from HS and allowed for reconstructed egg-box structures. Thus, recovering the HS-released reabsorbable Ca2+, which is disallowed by EGTA, to form Ca2+-pectate through PME activities is important for cell wall remodeling to prevent cell separation and retain plasma membrane integrity, and for coordinating with HS signaling in acquisition of thermotolerance in plants.鈣離子熱休克熱休克蛋白質果膠果膠酯酵素Ca2+Egg-box structureHeat shockPectinPectin methylesterasesThermotolerance