Effect of Ethylene Antagonists on Auxin-induced Inhibition of Intact Primary Root Elongation in Maize(Zea mays L.)

Kim, Soon Young,Mulkey, Timothy J. 한국식물학회 1997 Journal of Plant Biology Vol.40 No.4

Root elongation was measured in intact primary roots of maize (Zea mays L.) using a computerized root auxanometer. We examined the fact that root elongation was inhibited by auxin-induced ethylene production. Inhibition of root elongation was closely correlated with the concentrations of the exogenously applied auxin. Auxin-induced inhibition of root elongation was reversed by pretreatment or posttreatment of ethylene biosynthesis antagonists such as aminoethyoxyvinylglycine (AVG) and silver ions (Ag^2+). The magnitude of recovery effect was dependent on auxin concentrations. Root elongation was inhibited by adding ethylene producing agents such as 1-aminocyclopropane-1-carboxylic acid (ACC) and Ethephon. ACC- and Ethephon-induced inhibition of root elongation was reversed by blocking ethylene biosynthesis or activity. These data suggested that ethylene was involved in auxin-induced inhibition of root elongation and inhibition of root elongation by applied auxin, at least in part, was a reversible process.

Effect of Auxin and Ethylene on Elongation of Intact Primary Roots of Maize(Zea mays L.)

Kim, Soon Young,Mulkey, Timothy J. 한국식물학회 1997 Journal of Plant Biology Vol.40 No.4

We tested that the hypothesis that root elongation might be controlled by altering the level of ethylene in intact primary roots of maize (Zea mays L.). We measured root elongation in a short period using a computerized root auxanometer. Compounds which regulate ethylene production were applied to intact primary roots in different time periods. Root elongation was stimulated by the treatment with ethylene antagonists such as Co^2+, aminoethoxyvinylglycine (AVG) and L-canaline. This result suggested that root elongation was closely related to ethylene level of intact primary roots. Furthermore, IAA- and 1-aminocyclopropane-1-carboxylic acid (ACC)-induced inhibition of root elongation was reversed by treatment with Co^2+. The application of ACC to roots which have been exposed to IAA and Co^2+ have no significant effect on root elongation. However, the inhibition of root elongation by ACC in roots previously treated with IAA and AVG became manifest when the applied IAA concentrations were lower. These results were consistent with the hypothesis that the level of ethylene in intact roots functions to moderate root elongation, and suggested that auxin-induced inhibition of root elongation results from auxin induced promotion of ethylene production.

Effect of Ascorbic Acid on the Gravitropic Response of Primary Roots in Maize

Chung Su Kim(김충수),Timothy J. Mulkey,Soon Young Kim(김순영) 한국생명과학회 2014 생명과학회지 Vol.24 No.12

Ascorbic acid (AA)는 식물 발달과 생장에 필수적인 다기능성 대사산물이다. 본 연구에서는 항산화제인 AA가 옥수수 일차 뿌리에서 굴중성 반응에 미치는 효과를 조사하였다. 10-3 M AA를 신장대에 처리하면 뿌리 굴중성 반응은 영향을 받지 않고 뿌리 생장은 약간 억제되었다. 그러나 10-5 M과 10-3 M AA를 뿌리 끝에 처리하였을 때, 뿌리 굴중성 반응은 촉진된 반면, 뿌리 생장은 억제되었다. 수평으로 놓인 뿌리의 윗면과 아랫면에서 IAA함량의 차이는 차등 생장을 유발한다. 뿌리는 IAA에 대하여 매우 민감하여 아랫면에 증가된 IAA는 뿌리 생장을 억제한다. 그러므로 본 연구에서 AA가 존재할 때 IAA의 효과를 조사하였다. AA는 IAA와 함께 처리하면 굴중성 반응을 더욱 억제시켰다. 뿌리 생장과 굴중성 반응의 조절에 관여하는 AA의 작용을 알아보기 위하여, AA를 처리한 후 에틸렌 생성을 측정하였다. AA는 ACC가 에틸렌으로 전환되는 단계를 조절하는 ACC oxidase gene을 활성화시켜 에틸렌 생성을 촉진하였다. 이 결과는 AA가 에틸렌 작용의 조절을 통하여 옥수수 뿌리에서 굴중성 반응에 영향을 준다는 것을 제시한다. Ascorbic acid (AA) is a multifunctional metabolite in plants that is essential for plant development and growth. We examined the effect of AA, an antioxidant, on the gravitropic response of primary roots in maize. The application of 10-3 M AA to the elongation zone did not affect the gravitropic response and slightly inhibited the root growth. However, treatment with both 10-5 M and 10-3 M AA at the root tip increased the gravitropic response and inhibited root growth. Differences in indole-3- acetic acid (IAA) activity between the upper and lower hemispheres of the root resulted in differential elongation along the horizontal root. Roots are extremely sensitive to IAA, and increasing the amount of IAA in the lower hemisphere of the root inhibited elongation. Therefore, we examined the effect of IAA in the presence of AA. The inhibitory effect of AA on the gravitropic response was greater in combination with IAA. To understand the role of AA in the regulation of root growth and the gravitropic response, we measured ethylene production in the presence of AA in the primary roots of maize. AA stimulated ethylene production via the activation of the 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase gene, which regulates the conversion of ACC to ethylene. These results suggest that AA alters the gravitropic response of maize roots through modification of the action of ethylene.

Effect of Oryzalin on the Gravitropic Response and Ethylene Production in Maize Roots

Chungsu Kim(김충수),Timothy J. Mulkey(티모시 멀키),Jong-Sik Kim(김종식),Soon Young Kim(김순영) 한국생명과학회 2015 생명과학회지 Vol.25 No.11

Oryzalin은 미세소관을 분열시키는 dinitroaniline계의 제초제이다. 미세소관과 미세섬유는 평형석 침강과 세포벽을 구성하는 세포골격들이다. 평형석은 뿌리 끝에 있는 columella 세포에서 중력 인지 조절을 한다. 본 연구는 oryzalin이 옥수수 일차 뿌리에서 ethylene 생성을 통하여 굴중성 반응에 미치는 영향을 연구하였다. 뿌리 끝 부분에 10<SUP>-4</SUP> M oryzalin의 처리는 뿌리 성장과 굴중성 반응을 저해하였으나, 신장대에 처리하게 되면 저해현상은 관찰되지 않았다. 10<SUP>-4</SUP> M oryzalin을 뿌리 끝에 15시간 처리하면 뿌리 끝의 생장이 억제되고 둥근 형태로 부풀었다. 에틸렌의 전구물질인 ACC를 뿌리 끝에 처리하여도 굴중성 반응이 억제되었다. Oryzalin의 작용과 에틸렌 생성에 대한 관련성을 연구하기 위하여 oryzalin 처리 후 에틸렌 생성을 측정하였다. Oryzalin 처리에 의해 ACC oxidase와 ACC synthase의 활성이 증가되어 에틸렌 생성이 촉진되었다. Oryzalin은 ACO와 ACS의 유전자의 발현도 증가 시켰다. Indole-3-acetic acid (IAA)는 굴중성 반응 동안 관찰되는 비 대칭적 신장에 중요한 역할을 한다. 이러한 연구 결과는 oryzalin이 뿌리 끝에서 IAA transport를 억제하여 뿌리 신장대의 윗면과 아랫면의 IAA 양의 차이를 감소시키고, 또한 에틸렌 생성을 촉진하며 미세소관의 배열을 방해하여 뿌리 글중성과 생장을 억제할 가능성을 제시하고 있다. Oryzalin is a dinitroaniline herbicide, which disrupts the arrangement of microtubules. Microtubules and microfilaments are cytoskeletal components that are thought to play a role in the sedimentation of statoliths and the formation of cell walls. Statoliths regulate the perception of gravity by columella cells in the root tip. To determine the effect of oryzalin on the gravitropic response, ethylene production in primary roots of maize was investigated. Treatment with 10<SUP>-4</SUP> M oryzalin to the root tip inhibited the growth and gravitropic response of the roots. However, the treatment had no effect on the elongation zone of the roots. An application of 10<SUP>-4</SUP> M oryzalin for 15 hr to the root tip caused root tip swelling. The application of 1-aminocycopropane-1-carboxylic acid (ACC), a precursor of ethylene, to the root tip also inhibited the gravitropic response. To understand the role of oryzalin in the regulation of the growth and gravitropic response of roots, ethylene production in the primary roots of maize was measured following treatment with oryzalin. Oryzalin stimulated ethylene production via the activation of ACC oxidase (ACO) and ACC synthase (ACS), and it increased the expression of ACO and ACS genes. Indole-3-acetic acid (IAA) played a key role in the asymmetric elongation rates observed during gravitropism. The results suggest that oryzalin alters the gravitropic response of maize roots through modification of the arrangement of microtubules. This might reduce the distribution of IAA in the upper and lower sides of the elongation zone and increase ethylene production, thereby inhibiting growth and gravitropic responses.

EFFECTS OF ABSCISIC ACID AND XANTHOXIN ON ELONGATION AND GRAVITROPISM IN PRIMARY ROOTS OF ZEA MAYS

LEE, JUNE S.,HASENSTEIN, KARL-HEINZ,MULKEY, TIMOTHY J.,YANG, RICK L.,EVANS, MICHAEL L. 이화여자대학교 생명과학연구소 1990 생명과학연구논문집 Vol.1 No.-

We examined the involvement of abscisic acid(ABA) and xanthoxin(Xan)in maize root gravitropism by(1) testing the ability of ABA to allow positive gravitropism in dar-grown seedling of the maize cultivar LG11, a cultivar known to require light for positive gravitropism of the primary root,(2) comparing survature in roots in which half of the cap had been excised and replaced with agar containing either ABA or indole-3-acetic acid(IAA),(3)measuring gravitropism in roots of seedings sub merged in oxygenated solutions of ABA or IAA and (4) testing the effect of Xan on root elongation. Using a variety of methods of applying ABA to the root, we found that ABA did not cause horizontally-oriented primary roots of dark-grown seedings to become positively gravitropic. Replacing half of the root cap of vertically oriented roots with an agar block containing ABA had little or no effect on curvature relative to that of controls in which the half cap was replaced by a plain agar block Replacement of the removed half cap with IAA either canceled or reversed the curvature displayed by controls. When light grown seedings were submerged in ABA they responded strongly to gravistimulation while those in IAA did not. Xan(up to 0.1mM)did not affect root elongation. The results indicate that ABA is not a likely mediator of root gravitropism and that the putative ABA precursor, Xan, lacks the appropriate growth-inhibition properties to serve as a mediator of root gravitropism.