Rapid Inhibition of Auxin-induced Elongation of Avena Coleoptile Segments by Cordycepin

Abstract

The effects of cordycepin (3'-deoxyadenosine), an RNA synthesis inhibitor, on auxin-induced elongation in Avena coleoptile segments were studied with a position-sensing transducer. Cordycepin rapidly inhibited auxin-stimulated growth in the coleoptile segments whether added before, at the same time as, or after, the 2 jtM auxin treatment. Midcourse In mammalian cells, cordycepin has a much smaller inhibitory effect on the synthesis of heterogenous nuclear RNA than has actinomycin D (13), and it has been shown that the posttranscriptional addition of poly A (150-200 residues of adenylic acid) to heterogeneous nuclear RNA is much more sensitive to cordycepin than to actinomycin D (9). Experimentally, it has been found that cordycepin inhibits the arrival of mRNA to the polyribosomes in the cytoplasm. Cordycepin has also been reported (18) to inhibit the synthesis of ribosomal and transfer RNA in HeLa cells.Little use has been made of cordycepin with plant systems (2,7,12,19). Nooden (12) reported that 5 mm cordycepin caused a 50% decrease in growth of corn coleoptiles within I hr. Stockert et al. (19) found that 0.1 mm cordycepin caused nearly 80% of nucleoli to exhibit segregation within 2 hr in meristematic cells (22nd hr, 0.1% caffeine-induced binucleate cells) of A llium cepa root tips. They concluded that this nucleolar aberration was probably related to the effect of cordycepin on RNA synthesis. In unpublished studies (M. Cline) there is evidence that cordycepin inhibition of RNA synthesis in plant systems is general for all species of RNA.The present experiments were carried out with a high resolution continuous growth measuring apparatus to determine the effects of cordycepin, an RNA synthesis inhibitor, on auxin-promoted elongation in Avena coleoptile segments. MATERIALS AND METHODSAn angular position-sensing transducer was used to measure continuous elongation in 4-to 5-day-old coleoptile segments of Avenia sativa L. cv. Victory as described previously (15). Ten 1-cm segments, with primary leaves removed, were strung vertically on a wire and immersed in a measuring chamber containing 5 mM succinate buffer, pH 6.0. After a 1-hr equilibration period in the buffer solution, the coleoptile segments were treated with 2 fiM auxin and/or cordycepin in a buffered solution, as indicated under "Results." Cordycepin was purchased from Sigma Chemical Co.Mitochondria were isolated from 4-day-old etiolated mung bean shoots (Phaseolus aureus L.) by standard isolation procedures. Approximately 100 g of shoots were placed in 200 ml of grinding media containing: 0.4 M mannitol, 50 mM trisTricine (pH 7.4), 1 mg/ml BSA, 5 mm EDTA, and 4 mM cysteine. The shoots were disrupted with Moulinex mixer for 15 sec, and the solution was passed through a nylon mesh cloth. The suspension was centrifuged at 600g for 10 min, and 160 www.plantphysiol.org on May 10, 2018 -Published by Downloaded from

Inhibition of Acid-Enhanced Elongation of Zea mays Root Segments by Galactose

“…A protein factor is thought to take part in cell wall extension in acidic environments, since the pretreatment of stem segments with boiling water or with protease ( 17) reduced in vitro extension of pea epicotyl segments under acidic condition. Cycloheximide and cordycepin inhibit auxin-induced elongation (2,4,(22)(23)(24) and proton extrusion (2). The present results show that cycloheximide inhibits the acid-enhanced elongation as strongly as galactose, an observation that suggests that acid-enhanced elongation itself might depend, again, at least partially, on the synthesis of proteins that participate in cell wall metabolism.…”

Organ‐specific, developmental, hormonal and stress regulation of expression of putative pectate lyase genes in Arabidopsis

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“…We have estimated the half-life of phyA mRNA using the RNA synthesis inhibitor cordycepin (Cline and Rhem, 1974;Schopfer, 1989). These experiments show that the half-life of phyA mRNA is ~1 hr before red light treatment in etiolated oat seedlings.…”

“…We used cordycepin, a chain-terminating adenosine analog (Cline and Rhem, 1974;Schopfer, 1989), to inhibit RNA synthesis. Preliminary studies revealed that virtually all of the phyA mRNA hybridizing to the pAPSX2.7 antisense RNA probe was localized in the coleoptile of 4-day-old etiolated oat seedlings (K. Seeley and J. Colbert, manuscript in preparation).…”