DNA sequences of the 5' end of the chloroplast ndhF gene for 15 species of Caryophyllaceae have been analyzed by parsimony and neighbor-joining analyses. Three major clades are identified, with little or no support for monophyly of traditionally recognized subfamilies. The first of the three major clades identified (Clade I) is constituted by part of the subfamily Paronychioideae. It includes members of the tribe Paronychieae and members of tribe Polycarpeae. The second (Clade II) contains members of the Paronychieae exclusively. Tribe Paronychieae is thus apparently polyphyletic and tribe Polycarpeae is at least paraphyletic. The third clade (Clade III) includes members of subfamilies Alsinoideae and Caryophylloideae along with the genus Spergularia. The genus Scleranthus is also part of Clade III, while Drymaria groups with the other genera of tribe Polycarpeae in Clade II. We conclude that morphological characters previously used to delimit subfamilial groupings in the Caryophyllaceae are apparently unreliable estimators of phylogeny.

Myb-class transcription factors implicated in cell shape regulation were overexpressed in Arabidopsis thaliana and Nicotiana tabacum in an attempt to assess the extent to which cellular differentiation programs might be shared between these distantly related plants. GLABROUS 1, a myb gene required for trichome development in Arabidopsis, did not alter the trichome phenotype of the tobacco plants in which it was overexpressed. MIXTA, which in Antirrhinum majus is reported to regulate certain aspects of floral papillae development, did not complement the glabrous 1 mutant of Arabidopsis. However, 35S:MIXTA transformants of N. tabacum displayed various developmental abnormalities, most strikingly production of supernumerary trichomes on cotyledons, leaves and stems. In addition, floral papillae were converted to multicellular trichomes. CotMYBA, a myb gene which is expressed in Gossypium hirsutum ovules and has some homology to MIXTA, was also overexpressed in the two species. A similar but distinct syndrome of abnormalities, including the production of cotyledonary trichomes, was observed in 35S:CotMYBA tobacco transformants. However, CotMYBA did not alter trichome production in Arabidopsis. These results suggest that the trichomes of Arabidopsis and Nicotiana are merely analogous structures, and that the myb genes regulating their differentiation are specific and separate.

The pulse radiolysis of the proteolytic enzyme papain has been studied in nitrogen-purged and N2O-purged aqueous solutions at pH 6.4. The rate constant for reaction of OH with papain is 4.7 × 1010 M−1 s−1. The initial spectrum of the intermediate formed by this radical is consistent with a major fraction of attack at tyrosine residues with smaller proportions reacting at tryptophan and other sites. Subsequent spectral changes are also consistent with the preferential attack of OH on tyrosine. The overall rate constant for reaction of [Formula: see text] with papain is 4.1 × 1010 M−1 s−1 and the spectrum of the electron adduct closely resembles that of the disulfide anion [Formula: see text] However, there is evidence that not all reactions of [Formula: see text] with papain lead to the formation of this species. The results are discussed in the light of deactivation yields for Co60γ radiolysis measured by biochemical techniques.

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