The mRNA from the Sesbania rosfrafa early nodulin gene SrEnod2 accumulates in response to cytokinin application. Nuclear run-on assays using isolated root nuclei have shown that this accumulation occurs posttranscriptionally, and northern blot analysis of nuclear and total RNA levels revealed that it occurs primarily in the cytoplasm and not in the nucleus. After cytokinin enhancement of SrFnod2 mRNA accumulation and the subsequent removal of cytokinin, the levels of SrEnod2 mRNA did not return to basal levels, but oscillated over a 36-h time course. Application of the translational inhibitor cycloheximide was found to inhibit the enhancement of SrEnod2 mRNA accumulation by cytokinin and to cause its rapid decay. Okadaic acid and staurosporine, inhibitors of protein phosphatases and kinases, respectively, also inhibited cytokinin enhancement of SrEnod2 mRNA accumulation. In addition, okadaic acid was found to cause a decrease in SrEnodZ mRNA levels. These results provide evidence for a posttranscriptional mechanism of cytokinin enhancement of SrFnod2 mRNA accumulation, which appears to require concurrent protein synthesis, to involve protein phosphatases and kinases, and to occur primarily in the cytoplasm of the plant cell.

Higher-order optimized upwind schemes based on the Dispersion-Relation-Preserving (DRP) method are developed and tested for the first-order linear wave equation. The numerical results show that the optimized upwind DRP scheme has less dissipation and/or dispersion errors than that of the standard sixth-order upwind scheme and the central DRP scheme. The advantage of the upwind DRP scheme becomes even greater for simulating short waves or waves with discontinuous initial waveform.