Localized laccase activity modulates distribution of lignin polymers in gymnosperm compression wood

The woody stems of coniferous gymnosperms produce specialised compression wood to adjust the stem growth orientation in response to gravitropic stimulation. During this process, tracheids develop a compression-wood-specific S2L cell wall layer with lignins highly enriched with p-hydroxyphenyl (H)-type units derived from H-type monolignol, whereas lignins produced in the cell walls of normal wood tracheids are exclusively composed of guaiacyl (G)-type units from G-type monolignol with a trace amount of H-type units. We show that laccases, a class of lignin polymerisation enzymes, play a crucial role in the spatially organised polymerisation of H-type and G-type monolignols during compression wood formation in Japanese cypress (Chamaecyparis obtusa). We performed a series of chemical-probe-aided imaging analysis on C. obtusa compression wood cell walls, together with gene expression, protein localisation and enzymatic assays of C. obtusa laccases. Our data indicated that CoLac1 and CoLac3 with differential oxidation activities towards H-type and G-type monolignols were precisely localised to distinct cell wall layers in which H-type and G-type lignin units were preferentially produced during the development of compression wood tracheids. We propose that, not only the spatial localisation of laccases, but also their biochemical characteristics dictate the spatial patterning of lignin polymerisation in gymnosperm compression wood

An RNA aptamer with potent affinity for a toxic dimer of amyloid β42 has potential utility for histochemical studies of Alzheimer's disease

Oligomers of β-amyloid 42 (Aβ42), rather than fibrils, drive the pathogenesis of Alzheimer's disease (AD). In particular, toxic oligomeric species called protofibrils (PFs) have attracted significant attention. Herein, we report RNA aptamers with higher affinity toward PFs derived from a toxic Aβ42 dimer than toward fibrils produced from WT Aβ42 or from a toxic, conformationally constrained Aβ42 variant, E22P–Aβ42. We obtained these RNA aptamers by using the preincubated dimer model of E22P–Aβ42, which dimerized via a linker located at Val-40, as the target of in vitro selection. This dimer formed PFs during incubation. Several physicochemical characteristics of an identified aptamer, E22P–AbD43, suggested that preferential affinity of this aptamer toward PFs is due to its higher affinity for the toxic dimer unit (KD = 20 ± 6.0 nm) of Aβ42 than for less-toxic Aβ40 aggregates. Comparison of CD data from the full-length and random regions of E22P–AbD43 suggested that the preferential binding of E22P–AbD43 toward the dimer might be related to the formation of a G-quadruplex structure. E22P–AbD43 significantly inhibited the nucleation phase of the dimer and its associated neurotoxicity in SH-SY5Y human neuroblastoma cells. Of note, E22P–AbD43 also significantly protected against the neurotoxicity of WT Aβ42 and E22P–Aβ42. Furthermore, in an AD mouse model, E22P–AbD43 preferentially recognized diffuse aggregates, which likely originated from PFs or higher-order oligomers with curvilinear structures, compared with senile plaques formed from fibrils. We conclude that the E22P–AbD43 aptamer is a promising research and diagnostic tool for further studies of AD etiology

針葉樹仮道管における細胞壁成分の堆積

京都大学0048新制・課程博士農学博士甲第3228号農博第431号新制||農||399(附属図書館)学位論文||S60||N1544(農学部図書室)UT51-60-B98京都大学大学院農学研究科林産工学専攻(主査)教授 原田 浩, 教授 樋口 隆昌, 教授 葛西 善三郎学位規則第5条第1項該当Kyoto UniversityDFA

ワイヤー挿入および染料注入による道管ネットワークの追跡

広葉樹に特徴的な組織である道管は, 軸方向に非常に長いため追跡するのが困難である。これまで, その3次元的な解析には連続切片の作製など, 非常に手間のかかる手法がとられてきた。本研究では, 道管の内腔に細いワイヤーを挿入する手法と, 染料を注入する手法により道管のネットワークを定量的に解析することを試みた。これらの方法では, 軸方向に5cm以上離れた両木口面での道管の位置を一本一本追跡できた。ワイヤー挿入は径の大きく, 比較的通直な道管についての調査に適している。この方法は, 辺材部だけではなく, 一般にチロースにより閉塞されている心材部の道管の解析にも適用できる。一方, 染料の注入は大きい径の道管は言うまでもなく, 環孔材の晩材部の道管のように径の小さな道管にも有効である。しかし, ワイヤーの挿入とは異なり, チロースによって閉塞された道管の追跡は不可能である。染料の注入は, 樹脂鋳型法を併用することによりさらに有効なものとなる。これらの手法を基に, 道管ネットワークの3次元解析についてこれまで行われてきた非常に手間のかかる手法が, 大きく改善されることが期待される。Vessels, which characterize the hardwood, are too long to be traced along their longitudinal direction. The actual three-dimensional analysis is very troublesome procedure, although some methods such as serial sections have been tried. New methods, that is, insertion of thin wire and injection of pigments into vessel lumens, were proposed for the quantitative analysis of the network. By these methods, vessels could be identified one by one on both ends which were cut transversely at the distance of 5 cm or longer. Wire insertion was fit to investigate the specimen of which vessels were large in diameter and relatively straight, and applicable to not only sapwood but heartwood vessels which were generally plugged by tyloses. On the contrary, pigment injection was very effective to the smaller vessels, to say nothing of larger ones. However, the plugged vessels which were common in the heartwood were impossible to be injected by pigments. Pigment injection was also shown to be very useful when it was combined with the resin casting. The troublesome procedures of three-dimensional analysis on the vessel network are expected to be improved dramatically by these methods

<Preliminary>The Role of Extractives Involved in the Natural Durability of Domestic Softwood

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