Action of malformin A1 on gravitropic curvature in primary roots of maize (Zea mays L.)

Abstract

Malformins, a small family of cyclic pentapeptides, are active plant growth regulators isolated from the fungus Aspergillus niger. We purified malformin A1 from the crude malformin A mixture, and studied its action in the gravitropic response of maize roots. Intact primary roots that had been pretreated vertically with malformin A1 were placed in a humidified box in the horizontal position. Positive curvature (downward) was inhibited in the pretreated roots compared with the control. In addition, we measured the lateral transport of IAA in primary roots. Roots pretreated with malformin A1 did not show asymmetric distribution of IAA between the upper and lower sides of the elongation zone. Malformin A~ also stimulated ethylene production in maize root segments. Our results had suggested that maiformin A1 might inhibit the lateral transport of IAA across the roots from the upper to the lower side because of an increased level of ethylene. Therefore, we placed more IAA on the upper side at the initial phase of gravistimulation. These results were consistent with malformin Al-pretreated roots showing inhibited positive gravitropic curvature.

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

“…Lee et al [7] suggested that ethylene may modify positive curvature in the primary roots of maize by affecting gravity induced-lateral auxin transport. Kim et al [6] suggested that an optimal concentration of ethylene might be required for the regulation of gravitropism in maize roots. Yuan et al [20] reported that cortical microtubule reoriented in wounding stem in pea from transverse to vertical orientation.…”

“…Several factors regulate these two enzymes, especially auxin which stimulates the ethylene production through increasing the expression level of the ACS gene [21]. There are findings that ethylene regulates the root growth and gravitropism via alteration of auxin transport [6,13], and ethylene is required for root penetration in soil with auxin [14].…”

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

“…Lee et al [15] suggested ethylene may modify positive curvature in the primary roots of maize by affecting gravity induced-lateral auxin transport. Kim et al [14] suggested that an optimal concentration of ethylene might be required for the regulation of gravitropism in maize roots. Based on these results, AA may affect the gravity induced-lateral IAA transport in maize root resulting in the inhibition of curvature by AA in the presence of IAA.…”

“…Several factors regulate these two enzymes, especially auxin which stimulates the ethylene production through increasing the expression level of the ACS gene [25]. There are findings that ethylene regulates the root growth and gravitropism via alteration of auxin transport [14,21], and ethylene is require for root penetration in soil with auxin [22].…”