Red light causes a reduction in IAA levels at the apical tip by inhibiting de novo biosynthesis from tryptophan in maize coleoptiles

Abstract

When maize coleoptiles were unilaterally exposed to red light (7.9 micromol m(-2)s(-1) for 5 min), 3 h after treatment IAA levels in coleoptiles decreased in all regions, from top to basal, with levels about 60% of dark controls. Localized irradiation in the 5 mm top zone was sufficient to cause the same extent of IAA reduction in the tips to that in the tips of whole irradiated shoots. When coleoptiles were treated with N-1-naphthylphthalamic acid (NPA), an accumulation of IAA in the tip and a decrease of diffusible IAA from tips were simultaneously detected. IAA accumulation in red-light treated coleoptiles by NPA was much lower than that of dark controls. NPA treatment did not affect the content of conjugated IAA in either dark or light treated coleoptile tips. When (13)C(11) (15)N(2)-tryptophan (Trp) was applied to the top of coleoptiles, substantial amounts of stable isotope were incorporated into free IAA in dark and red-light treated coleoptile tips. The ratio of incorporation was slightly lower in red-light treated coleoptile tips than that in dark controls. The label could not be detected in conjugated IAA. The rate of basipetal transport of IAA was about 10 mm h(-1) and the velocity was not affected by red light. These results strongly suggest that red light does not affect the rates of conversion of free IAA to the conjugate form or of the basipetal transport, but just reduces the IAA level in the tips, probably inhibited by IAA biosynthesis from Trp in this region.

Development of an in vitro System for the Evaluation of Allelopathic Activities of Asparagus Calluses

“…Recently, understanding of the plant physio- logical or developmental outcomes caused by light quality has increased (Folta and Maruhnich, 2007;Galen et al, 2007;Nishimura et al, 2006). Interesting experimental results have demonstrated that significant differences in the traits of horticultural relevance of diploid strawberry plants were observed under a blue/ red light mixture conditions (Folta and Childers, 2008).…”

NAL1 allele from a rice landrace greatly increases yield in modern indica cultivars

“…S9) by gas chromatographyselected ion monitoring-mass spectroscopy (GC-SIM-MS) as described (45,46). To investigate polar IAA transport in IR64 and NIL-SPIKE coleoptiles, we applied 3 μM IAA to the top of coleoptile sections (1.5-3.0 mm) for 30 min, then incubated the coleoptiles on an agar block for 10 min and measured the transported IAA by GC-SIM-MS as above.…”

Hormonal Regulation of Lateral Root Development in Arabidopsis Modulated byMIZ1and Requirement of GNOM Activity forMIZ1Function

“…IAA purification and measurement were performed as described previously by Nishimura et al (2006) with the following minor modifications. To extract free IAA from tissues, 6-d-old Arabidopsis roots (10-35 mg fresh weight) were placed in 2.0-mL tubes with 180 mL of cold 80% methanol containing 0.1 mg mL 21 2,6-di-tert-butyl-4-methylphenol and 2.0 to 4.0 ng of [ 13 C 6 ]IAA (Cambridge Isotope Laboratories) as well as a small amount of glass beads.…”