高低温催青温度敏感期家蚕卵的差异蛋白筛查

滞育（Diapause）是昆虫发育停滞或减缓的生理状态,家蚕Bombyx mori作为卵滞育的代表,其滞育过程已得到广泛研究,但诱导滞育发生的分子机制尚不清楚。二化性家蚕滞育性由遗传和母系在胚胎期所处的环境条件决定,25℃催青蚕卵孵化后的家蚕产滞育卵,15℃低温催青则诱导家蚕产下非滞育卵。本研究分别用25℃和15℃催青蚕卵,在发生滞育诱导的温度敏感期取样,抽提蛋白质通过非标（Label-free）蛋白质组定量技术进行质谱测序。筛选出具有明显表达差异的蛋白104个,其中56个蛋白上调,48个蛋白下调。通过生物信息学对差异蛋白进行GO分类和KEGG功能富集分析,结果显示差异蛋白主要参与生长发育、物质代谢和胁迫应答等生物过程;同时差异蛋白主要参与胰岛素信号通路、乙醛酸和二羧酸代谢等相关途径。分别选取上调基因和下调基因进行qRT-PCR验证,其趋势与蛋白组学结果一致。该研究将为进一步解析家蚕滞育诱导发生机制提供靶标蛋白和数据参考。     

即时浸酸显著降低滞育家蚕卵的还原型与氧化型谷胱甘肽比值

即时浸酸在阻止家蚕Bombyx mori卵滞育发动的同时, 显著提高了家蚕卵H₂O₂含量。还原型谷胱甘肽（reduced glutathione, GSH）与氧化型谷胱甘肽（oxidized glutathione, GSSG）的比值是一种氧化胁迫状态的动态指标。为了调查即时浸酸是否造成滞育家蚕卵氧化胁迫, 本研究利用分光光度法分别测定了滞育家蚕卵和5 min即时浸酸滞育家蚕卵中GSH和GSSG含量以及谷胱甘肽转移酶（glutathione-S-transferase, GST）活性。结果表明: 处理后24 h, 即时浸酸处理家蚕卵的总谷胱甘肽（GSH+2GSSG）含量、 GSH含量、 GSSG含量、 GSH/GSSG比值和GST活性分别相当于同期滞育家蚕卵的204%, 78%, 550%, 14%和97%。据此推测, 即时浸酸在阻止滞育发动的同时, 可能通过促进GSH氧化为GSSG, 而显著降低了GSH/GSSG比值, 使家蚕卵处于过氧化状态。     

环境条件诱导的家蚕滞育系与非滞育系中游离核苷酸的动态变化

家蚕二化性品种卵的滞育性是由亲代卵胚胎期接受的环境条件决定。在生物体中,ATP和UTP不仅是遗传物质的原料和能量物质,也是重要的信号分子,它们作为神经递质可以激活许多生理过程。本研究利用高压液相色谱(HPLC)检测了家蚕二化性品种大造刚孵化幼虫和终龄幼虫的游离核苷酸的含量。结果表明,预定次代产滞育卵[亲代卵高温(25℃)光照]比预定次代产非滞育卵[亲代卵低温(15℃)黑暗]的刚孵化幼虫整体特别是头部ATP和UTP含量高,并达到显著水平,随着发育到上簇阶段,这种差异显著增加。这些结果暗示,家蚕体内特别是头部游离核苷酸与由环境诱导的家蚕卵滞育性有关,为进一步研究家蚕脑对环境条件的接受、保持的机制提供了一条重要途径。     

家蚕胚胎发育中过氧化氢的代谢

过氧化氢（H2O2）是生物体内主要的活性氧来源之一。在超氧化物歧化酶（SOD）、过氧化氢酶（CAT）等的催化作用下,H2O2被降解,释放出活性氧。所以,生物个体发育过程中体内H2O2、SOD和CAT含量的变化反映着H2O2的代谢水平。另外,家蚕是蚕卵滞育昆虫,实验设计考虑到了滞育前后可能会有的差别。取产后10分钟内的卵为供试材料。采用即时浸酸法解除卵滞育。采用比色法和氧电极法测定并比较家蚕胚胎滞育形成与解除过程中过氧化氢的代谢。结果表明：（1）受精初期最低水平（Fig.2);（2）胚胎发育过程中（即时浸酸除滞有）,H2O2量除168－216h处于低水平外均显著高于滞育卵（Fig.3),SOD活性分别在72h、168h,形成大小两峰,后期显著高于滞育卵（Fig.4),而CAT活性72－192h保持平衡,随后急剧上升,前期显著低于滞育卵,后于滞育卵（Fig.4),而CAT活性72－192h保持平衡,随后急剧上升,前期显著低于滞育卵,后期相反（Fig.5);(3)滞育形成过程中H2O2水平变化平缓（Fig.6),SOD活性前期剧烈活动,但后期保持平稳（Fig.7),CAT活性逐步升高（Fig.8),而浸酸解除滞育过程中H2O2水平显著高于滞育卵（Fig.6),SOD活性前期出现新峰,后期显著升高（Fig.7),CAT活性显著低于滞育卵（Fig.8)。结合他人的研究结果,可以推测：家蚕卵H2O2代谢状况可能在其滞育形成和解除中具有重要意义,或许酯酶A4计器假说与卵孔堵塞说可以通过H2O2而联系起来。     

低温冷藏提高家蚕滞育卵NAD含量和胞质苹果酸脱氢酶活性

为了调查5℃低温处理是否改变家蚕Bombyx mori卵滞育NAD代谢, 本研究利用HPLC和分光光度法测定了经25℃和5℃分别处理的滞育卵中NADH 含量、 NAD⁺含量、 乳酸脱氢酶（LDH）活性和胞质苹果酸脱氢酶（cMDH）活性。结果表明： 5℃处理的NAD（NADH + NAD⁺）含量和cMDH活性分别增加了106%和53%, 并且显著高于25℃处理（P< 0.01）; 但是两种处理的NADH/NAD⁺比值和LDH活性没有显著差异（P> 0.05）。据此推测, 5℃低温处理加强了家蚕滞育卵NAD⁺合成和再生能力。     

过表达Grx1抑制HEK293T细胞中H2O2诱导的p38MAPK信号通路

谷氧还蛋白1（glutaredoxin1,Grx1）是细胞内一种重要的巯基 二硫键氧化还原酶,在细胞内氧化还原状态的调控及抵抗氧化应激损伤过程中发挥重要作用.为进一步探讨Grx1的抗氧化机制,本实验将重组质粒pcDNA3.1(+)-hGrx1瞬时转染HEK293T细胞,经RT-PCR和Western印迹验证,细胞转染后实现了Grx1的过表达;以不同浓度H₂O₂为损伤因素,建立细胞氧化应激模型,检测过表达Grx1后细胞存活率,丙二醛（MDA）含量,超氧化物歧化酶（SOD）活力和乳酸脱氢酶（LDH）漏出率的变化,观察过表达Grx1后细胞的抗氧化能力;用终浓度100 μmol/LH₂O₂作用于细胞,利用Western 印迹检测120 min内HEK293T细胞中p38MAPK磷酸化水平.实验结果表明,HEK293T细胞过表达Grx1后,缓解了细胞的氧化应激损伤;转染空载体组细胞p38MAPK磷酸化水平在H₂O₂刺激后5 min开始升高,15 min达到最高值,并可维持至120 min左右;而过表达Grx1组细胞p38MAPK磷酸化水平在H₂O₂刺激后各时间段没有明显改变,提示Grx1通过抑制H₂O₂诱导的p38MAPK信号通路激活发挥其抗氧化作用.     

家蚕滞育卵与非滞育卵中几种关键酶活性的比较

家蚕Bombyx mori是卵滞育的昆虫, 在滞育期间无形态变化, 也不存在器官发育和组织分化, 然而其生理代谢过程仍在进行。为进一步研究家蚕滞育的机制, 本研究测定了家蚕滞育卵、 即时浸酸处理的滞育卵及非滞育卵在胚胎发育过程中的超氧化物歧化酶(superoxide dismutase, SOD, EC 1.15.1.1)、 过氧化氢酶(catalase, CAT, EC 1.11.1.6)、 丙酮酸激酶(pyruvate kinase, PK, EC 2.7.1.40)、 乙酰胆碱酯酶(acetylcholine esterase, AchE, EC 3.1.1.7)和乳酸脱氢酶(lactate dehydrogenase, LDH, EC 1.1.1.28) 的活性变化。结果表明： 处理后1-7 d, 即时浸酸处理的滞育卵, SOD活性由56 517.00 U/g提高到81 986.94 U/g, CAT活性由14.98 U/g提高到106.90 U/g, PK活性由25.19 U/g提高到181.70 U/g, AChE活性由17.88 U/g提高到287.86 U/g, 而LDH活性由169.96 U/g下降到122.82 U/g。 而在非滞育卵中, SOD活性由86 417.99 U/g下降到66 024.19 U/g, LDH活性由169.07 U/g下降到135.02 U/g; CAT活性由1.47 U/g提高到44.37 U/g, PK活性由20.56 U/g提高到92.09 U/g, AChE活性由21.40 U/g提高到99.17 U/g。在滞育卵中, SOD和AChE活性较稳定; CAT活性随发育上升, 而LDH活性随发育而下降; PK活性在胚胎发育的前 4 d呈上升趋势, 随后基本保持稳定。通过了解家蚕滞育卵、 非滞育卵与即时浸酸卵的相关酶活性在胚胎发育过程中存在的变化, 有助于进一步揭示家蚕滞育的机理。     

维生素C保护Aβ1-40Cu(Ⅱ)复合物引起的神经元氧化损伤

老年斑中存在大量β 淀粉样蛋白（β-amyloid, Aβ）是老年痴呆症（Alzheimer′s disease, AD）的重要病理特征.大量数据表明,Aβ上具有与过渡态金属离子共价结合的位点,二者能结合成为寡聚复合物. Aβ_1-40Cu（Ⅱ）复合物通过Cu²⁺的还原催化O₂产生H₂O₂但反应机制不清.本文尝试以天然抗氧化剂维生素C（VC）来对抗Aβ_1-40及Aβ_1-40Cu（Ⅱ）复合物产生的H₂O₂对原代培养的神经细胞的毒性.结果表明,VC能够起到显著的保护作用,其有效浓度为1mmol/L.本文用胞外乳酸脱氢酶泄漏量和H₂O₂生成量的数据证实了细胞存活率（MTT实验）的实验结果.这些结果表明,Aβ_1-40Cu（Ⅱ）复合物能够释放更多的H₂O₂,引发细胞膜破裂并最终引起细胞死亡.加入VC后,神经元受到的损伤较轻,提示VC在保护细胞免受氧化损伤方面发挥了重要作用.     

镉胁迫对家蚕脂肪体脂质过氧化物含量及抗氧化酶活性和mRNA表达的影响

【目的】探讨鳞翅目模式昆虫家蚕Bombyx mori作为重金属污染的监测指示生物在镉胁迫下的酶反应及相关的基因表达。【方法】给家蚕幼虫期全龄添食镉(Cd²⁺), 调查不同性别家蚕5龄幼虫脂肪体中脂质过氧化物丙二醛（MDA）的含量, 超氧化物歧化酶（SOD）、 过氧化氢酶（CAT）和谷胱甘肽过氧化物酶（GSH-Px）的活性及其基因表达水平的变化。【结果】Cd²⁺胁迫对雌雄家蚕MDA 含量均具有浓度效应关系, MDA含量随Cd²⁺胁迫浓度的升高而增加。Cd²⁺胁迫下, SOD和CAT活性表现为先升后降的变化趋势, Pearson相关性分析显示SOD和CAT活性变化有显著相关性(雄: R=0.770, P=0.001; 雌: R=0.854, P=0.000）。雌性家蚕脂肪体中CAT活性变化和Cat mRNA水平的表达具有正相关性（R=0.712, P=0.003）。雄性家蚕脂肪体中GSH-Px活性随Cd²⁺胁迫浓度的升高而增加, 显示浓度 效应关系, 12.5~50 mg/kg Cd²⁺胁迫组GSH-Px活性与对照相比有显著差异（P<0.05）, 其活性和GSH-Px mRNA水平的表达具有正相关性（R=0.834, P=0.000）; 雌性家蚕脂肪体中GSH-Px活性表现为先升后降的变化趋势, 12.5 mg/kg Cd²⁺胁迫组GSH-Px活性与对照相比有显著增加（P<0.01）。【结论】结果表明, 急性镉胁迫对家蚕脂肪体有明显的毒性作用, 其作用机制与脂质过氧化加剧和抗氧化酶活性变化有关。家蚕对重金属镉的解毒机制有性别相关性。     

家蚕滞育性卵盐酸处理的靶物质

酯酶A4（EA4）是家蚕卵的滞育生物钟蛋白质。从家蚕C108品种产下后48 h的滞育性卵和盐酸活化处理卵分离纯化出EA4酶蛋白,使用合成的EA4活性多肽抑制因子PIN（氨基酸结构：SIFMTKQHSQ DDIIQHPLDY VEQQIHQQKQ KLQKQTLN）,研究了PIN对EA4酶蛋白的作用机制。滞育性卵的EA4酶蛋白和PIN在25℃混合24h后,用矩阵辅助激光解吸离子质谱法,检测到了二者的结合体,该结合体在盐酸处理后消失;盐酸活化处理蚕卵的EA4酶蛋白和合成PIN之间没有出现这种结合体。体外25℃,滞育性蚕卵EA4的ATPase特征性活性峰在6.5 h后出现,而盐酸活化处理蚕卵的EA4在1.5 h后出现活性峰值。盐酸处理可能通过解除PIN对EA4的抑制作用,在短时间内激活EA4酶蛋白,从而活化滞育性蚕卵。     

Genome‐wide microarray screening for Bombyx mori genes related to transmitting the determination outcome of whether to produce diapause or nondiapause eggs

The bivoltine silkworm Bombyx mori (Lepidoptera: Bombycidae) exhibits a maternally controlled embryonic diapause. Maternal silkworms decide whether to lay diapause or nondiapause eggs depending on environmental factors such as the temperature and photoperiod during the egg and larval stages, and then induce diapause eggs during the pupal stage. However, little is known about the molecular mechanism that conveys the outcome of whether to produce diapause or nondiapause eggs from the egg or larval stages to the pupal stage. This study used microarray analysis to investigate differentially expressed genes in the larval brains of diapause‐ and nondiapause‐egg producers, to which bivoltine silkworms were destined by thermal or photic stimulation during the egg stage. The cytochrome P450 18a1 and Krüppel homolog 1 genes were upregulated in producers of diapause eggs compared with those of nondiapause eggs under both experimental conditions. Cytochrome P450 18a1 encodes a key enzyme for steroid hormone inactivation and Krüppel homolog 1 is an early juvenile hormone‐inducible gene that mediates the repression of metamorphosis. The upregulation of these genes during the larval stage might be involved in the signaling pathway that transmits information about the diapause program from the egg stage to the pupal stage in the silkworm.     

Variation in glutathione status associated with induction and initiation of diapause in eggs of the bivoltine strain of the silkworm Bombyx mori

For the bivoltine (Dazao) strain of the silkworm Bombyx mori L., diapause expression in progeny is induced by exposure to conditions of 25 °C and continuous illumination (LL) during the maternal generation, whereas an environment of 15 °C and constant darkness (DD) results in nondiapause progeny. Initiation of diapause in progeny can be prevented by treatment of diapause‐programmed eggs with hydrochloric acid (HCl) at approximately 24 h post‐oviposition. To investigate whether glutathione is involved in the regulation of diapause induction and initiation in this species, measurements of total glutathione, reduced glutathione (GSH), oxidised glutathione (GSSG), GSH/GSSG ratio, glutathione S‐transferase (GST) and peroxiredoxins (Prdx) are compared in eggs incubated under LL and DD conditions, and between diapause eggs and those treated with HCl. Compared with DD, eggs incubated under LL have higher total glutathione (GSH + 2GSSG), lower GSH, higher GSSG, a lower GSH/GSSG ratio, lower GST activity and higher Prdx activity at stages 20–25 of maternal embryogenesis. The lower ratio of GSH/GSSG is indicative of pro‐oxidative conditions during diapause induction, which may result from the stronger oxidation of GSH. Compared with HCl‐treated eggs, diapause eggs have lower total glutathione, no difference in GSH, lower GSSG, a higher GSH/GSSG ratio, no difference in GST activity and lower Prdx between 36 and 72 h post‐oviposition. The higher ratio GSH/GSSG is indicative of reducing conditions during diapause initiation, which may a result of the weaker oxidation of GSH. Moreover, variations of Prdx and GST suggest that Prdx rather than GST plays an important role in the oxidation of GSH during the induction and initiation of diapause.     

Metabolism of hydrogen peroxide between diapause and non‐diapause eggs of the silkworm,Bombyx Mori during chilling at 5°C

When diapause and non‐diapause eggs of the same bivoltine strain of Bombyx mori were chilled at 5°C for more than 30 days, the hatchability of diapause eggs increased while that of non‐diapause eggs decreased, respectively. To investigate the relationship between effects of chilling on the hatchability and the metabolism of hydrogen peroxide (H₂O₂), content of H₂O₂ and activities of superoxide dismutase (SOD), xanthine oxidase (XO), and catalase (CAT) between diapause and non‐diapause eggs were determined during the chilling at 5°C. The significant enhancement of H₂O₂ occurred prior to the quick increase of the hatchability in diapause eggs and coincided with the quick decline of the hatchability in non‐diapause eggs, respectively. Diapause eggs contained significantly higher H₂O₂ and XO activity and lower CAT activity compared to non‐diapause eggs. Our results showed that there were significant differences in the metabolism of H₂O₂ between diapause and non‐diapause eggs during chilling and that significant enhancement of H₂O₂ may be involved in the diapause termination of diapause eggs and the cell damage of non‐diapause eggs. © 2010 Wiley Periodicals, Inc.     

Changes in glutathione redox cycle during diapause determination and termination in the bivoltine silkworm,Bombyx moil

To explore whether glutathione regulates diapause determination and termina tion in the bivoltine silkworm Bombyx mori, we monitored the changes in glutathione redox cycle in the ovary of both diapanse and nondiapauseegg producers, as well as those in dia pause eggs incubated at different temperatures. The activity ofthioredoxin reductase （TrxR） was detected in ovaries but not in eggs, while neither ovaries nor eggs showed activity of glutathione peroxidase. A lower reduced glutathione/oxidized glutathione （GSH/GSSG） ratio was observed in the ovary of diapauseegg producers, due to weaker reduction of oxidized glutathione （GSSG） to the reduced glutathione （GSH） catalyzed by glutathione reductase （GR） and TrxR. This indicates an oxidative shift in the glutathione redox cy cle during diapause determination. Compared with the 25℃treated diapause eggs, the 5℃treated diapause eggs showed lower GSH/GSSG ratio, a result of stronger oxidation of GSH catalyzed by thioredoxin peroxidase and weaker reduction of GSSG catalyzed by GR. Our study demonstrated the important regulatory role of glutathione in diapause determination and termination of the bivoltine silkworm.     

Silkworm strains that can be clearly destined towards either embryonic diapause or direct development by adjusting a single ambient parameter during the preceding generation

In the silkworm, Bombyx mori (Lepidoptera: Bombycidae), embryonic diapause is under maternal control and the decision between diapause and direct development in bivoltine strains depends on environmental factors such as temperature and photoperiod experienced by the preceding generation. We reared ten bivoltine silkworm strains (c10, g32, k06, n25, p21, p22, p24, p44, p50 and p63) under various thermal and light conditions and examined the incidence of embryonic diapause in the next generation to identify strains in which the incidence of diapause can be controlled within the range of 0 to 100% by adjusting a single ambient parameter. Some strains were clearly destined towards either diapause or direct development. The diapause incidence in the c10, p22 and p50 strains was controlled by temperature during the egg stage (0% at 18°C and 100% at 25°C), that in the p50 strain was also determined to be dependent on illumination during the egg stage (0% under continuous darkness and 100% under continuous illumination), and photoperiod during the larval stage regulated diapause in p44 and p50 (0% and 100% under long‐day and short‐day photoperiod, respectively), when all other external parameters remained constant under each experimental condition. These diapause‐controllable silkworm strains might serve as model systems for studies of insect diapause, especially for the differential screening of related factors.     

Expression of heat shock protein 70a mRNA in Bombyx mori diapause eggs

In an effort to understand whether heat shock protein 70 (Hsp70) participates in the environmental 5 °C signal reception/transduction toward breaking embryonic diapause of the silkworm Bombyx mori, we isolated a cDNA for Hsp70a and examined the expression of Hsp70a mRNA in B. mori diapause and nondiapause eggs by quantitative real-time PCR. Hsp70a mRNA gradually increased in diapause eggs continuously kept at 25 °C after oviposition to maintain diapause. When diapause eggs were exposed to the diapause-terminating condition of 5 °C beginning at 2 days post-oviposition, Hsp70a mRNA increased beginning at 5 days post-cold treatment. Even in nondiapause eggs, Hsp70a mRNA increased slightly with exposure to 5 °C. These results suggest that Hsp70a is involved in reception/transduction of the diapause-terminating (5 °C) signal via gene activation. The expression patterns of Hsp70a mRNA are discussed in relation to those of the cold-response gene Samui.     

Variations of hydrogen peroxide and catalase expression in Bombyx eggs during diapause initiation and termination

For diapause eggs of the silkworm, Bombyx mori, diapause initiation is prevented with hydrochloric acid (HCl) at around 20 h post-oviposition while diapause status is terminated with chilling around 5°C. To investigate whether hydrogen peroxide (H(2)O(2)) and catalase expression are involved in diapause initiation and termination, the concentration of H(2)O(2), relatively higher levels of catalase mRNA and activity of catalase were compared between (1) 20-h-old diapause eggs and the HCl-treated diapause eggs, and (2) 10-day-old diapause eggs and the 5°C-chilled diapause eggs. Compared to diapause eggs, the HCl-treated eggs had significantly higher H(2)O(2) concentrations (up from approximately 1-3 μmol/g fresh mass to 5-8 μmol/g fresh mass), higher relative level of catalase mRNA (up from 0 to 35.2%) and higher catalase activity (up from 2.51 units/mg protein to 4.97 units/mg protein) at 96 h post-treatment. On the other hand, the 5°C chilling resulted in significant increases of H(2)O(2) concentration (up from 0.79 μmol/g fresh mass to 5.57 μmol/g fresh mass), relative level of catalase mRNA (up from 0 to 71.4%) and catalase activity (up from 0.88 units/mg protein to 3.42 units/mg protein) within 120 days. The results obtained in this work suggest that variations of H(2)O(2) and catalase expression in Bombyx eggs are involved in diapause initiation and termination.     

Role of H2O2 and heme-containing O2 sensors in hypoxic regulation of tyrosine hydroxylase gene expression

In the currentstudy, we investigated links betweenO₂-regulatedH₂O₂formation and the hypoxic induction of mRNA for tyrosine hydroxylase(TH), the rate-limiting enzyme in catecholamine synthesis, inO₂-sensitive PC-12 cells. Duringexposure of PC-12 cells to 5% O₂,H₂O₂concentration decreased by 40% as measured with2',7'-dichlorofluorescein (DCF). Treatment withH₂O₂reduced TH mRNA during normoxia and prevented the induction of TH mRNAduring hypoxia. Treatment with catalase orN-(2-mercaptopropionyl)-glycine, areducing antioxidant agent that decreasesH₂O₂concentration, also induced TH mRNA. Deferoxamine (DF), an ironchelator, failed to affectH₂O₂formation but induced TH mRNA in normoxia and hypoxia.CoCl₂ led to a decrease inH₂O₂at 20 h of treatment but induced TH mRNA during normoxia and hypoxiabefore it affectedH₂O₂.In conclusion, TH gene expression correlates inversely withH₂O₂formation. DF and Co²⁺ seem toaffect TH gene expression in themechanism downstream from theH₂O₂formation rather than by interfering with theH₂O₂-generating activity of the O₂ sensor.

     

Studies on the change of the respiratory system in roots in relation to the growth of plants II. Activity of iron-containing oxidases in roots of cereal crops with the aging of plants

Distribution of iron-containing oxidases in aging nodal rootsof rice and wheat was studied. Activities of cytochrome c oxidase(1.9.3.1 [EC] , cytochrome c : O₂ oxidoreductase), catalase (1.11.1.6 [EC] ,H₂O₂: H₂O₂ oxidoreductase) and peroxidase (1.11.1.7 [EC] , donor:H₂O₂ oxidoreductase) in wheat roots were comparatively higherthan were those in rice roots at corresponding stages. Cytochromec oxidase in roots remained active throughout the lives of therice and wheat crops. In rice roots, catalase seemed to playa distinct role around the panicle formation stage. Decay ofcatalase activity took place earlier than did that of peroxidaseand cytochrome c oxidase activities. In wheat roots similarenzyme activity changes were not observed. Data may suggestthat the high activity of iron containing oxidases at the panicleformation stage (I) may be chiefly due to catalase activityin rice roots. ¹Paper presented at the 14th Annual Meeting of the Society ofthe Science of Soil and Manure, Japan (1968). (Received November 21, 1968; )