SummaryABCG11/WBC11, an ATP binding cassette (ABC) transporter from Arabidopsis thaliana, is a key component of the export pathway for cuticular lipids. Arabidopsis wbc11 T-DNA insertional knock-out mutants exhibited lipidic inclusions inside epidermal cells similar to the previously characterized wax transporter mutant cer5, with a similar strong reduction in the alkanes of surface waxes. Moreover, the wbc11 knock-out mutants also showed defects not present in cer5, including post-genital organ fusions, stunted growth and a reduction in cutin load on the plant surface. A mutant line previously isolated in a forward genetics screen, called permeable leaves 1 (pel1), was identified as an allele of ABCG11/WBC11. The double knock-out wbc11 cer5 exhibited the same morphological and biochemical phenotypes as the wbc11 knock-out. A YFP-WBC11 fusion protein rescued a T-DNA knock-out mutant and was localized to the plasma membrane. These results show that WBC11 functions in secretion of surface waxes, possibly by interacting with CER5. However, unlike ABCG12/ CER5, ABCG11/WBC11 is important to the normal process of cutin formation.

Most aerial surfaces of plants are covered by cuticular wax that is synthesized in epidermal cells. The wax mixture on the inflorescence stems of Arabidopsis (Arabidopsis thaliana) is dominated by alkanes, secondary alcohols, and ketones, all thought to be formed sequentially in the decarbonylation pathway of wax biosynthesis. Here, we used a reverse-genetic approach to identify a cytochrome P450 enzyme (CYP96A15) involved in wax biosynthesis and characterized it as a midchain alkane hydroxylase (MAH1). Stem wax of T-DNA insertional mutant alleles was found to be devoid of secondary alcohols and ketones (mah1-1) or to contain much lower levels of these components (mah1-2 and mah1-3) than wild type. All mutant lines also had increased alkane amounts, partially or fully compensating for the loss of other compound classes. In spite of the chemical variation between mutant and wild-type waxes, there were no discernible differences in the epicuticular wax crystals on the stem surfaces. Mutant stem wax phenotypes could be partially rescued by expression of wild-type MAH1 under the control of the native promoter as well as the cauliflower mosaic virus 35S promoter. Cauliflower mosaic virus 35S-driven overexpression of MAH1 led to ectopic accumulation of secondary alcohols and ketones in Arabidopsis leaf wax, where only traces of these compounds are found in the wild type. The newly formed leaf alcohols and ketones had midchain functional groups on or next to the central carbon, thus matching those compounds in wild-type stem wax. Taken together, mutant analyses and ectopic expression of MAH1 in leaves suggest that this enzyme can catalyze the hydroxylation reaction leading from alkanes to secondary alcohols and possibly also a second hydroxylation leading to the corresponding ketones. MAH1 expression was largely restricted to the expanding regions of the inflorescence stems, specifically to the epidermal pavement cells, but not in trichomes and guard cells. MAH1-green fluorescent protein fusion proteins localized to the endoplasmic reticulum, providing evidence that both intermediate and final products of the decarbonylation pathway are generated in this subcellular compartment and must subsequently be delivered to the plasma membrane for export toward the cuticle.

We examined the effects of light and surface hydrophobicity individually and in tandem on Hincksia irregularis (Kützing) Amsler spore settlement. Hincksia irregularis spores were determined to be negatively phototactic by the use of computer-assisted motion analysis. Spore settlement was significantly influenced by surface hydrophobicity and by light, individually and in tandem. Experiments conducted using culture plates modified to reduce well edge artifacts revealed significantly higher settlement on hydrophobic surfaces and in dark environments when compared with negatively charged surfaces and lighted environments. Experimental light/dark boundaries elicited distinct spore settlement responses, with spores displaying dissimilar settlement patterns on plates with different surface hydrophobicities. The results of this study indicate H. irregularis spores possess the capacity for complex responses to their environment. These complex responses may influence dispersal and aid spores in the detection of suitable settlement locations in marine microenvironments. Key index words: Hincksia irregularis ; macroalgal spore; motion analysis; phototaxis; settlement; surface hydrophobicityAbbreviations: ANOVA, analysis of variance; ASW, artificial seawater; RCD, rate of change of direction; REGWQ, Ryan-Einot-Gabriel-Welsch range post-hoc tests; SPEE, average spore speed 1

Three new steroidal sulfate pentaglycosides (asterosaponins), goniopectenosides A−C (1−3), were isolated from the polar extract of the starfish Goniopecten demonstrans. The pentasaccharide moiety linked to C‐6 of 3β‐sulfated steroidal aglycones, consists of D‐xylose, D‐fucose, D‐quinovose, and the unprecedented 3‐O‐methyl‐D‐quinovose. The three asterosaponins differ from each other in the side chains. Their structures were elucidated by extensive NMR experiments including 1H‐1H (COSY, TOCSY, ROESY) and 1H‐13C (HMQC and HMBC) spectroscopy as well as chemical evidence. The isolated asterosaponins have been found to significantly inhibit the settlement of the biofouling marine brown macroalga Hincksia irregularis.

Spores newly released from plurilocular sporangia of Ectocarpus siliculosus (Dillw.) Lyngb. sporophytes were assayed for chemotaxis to nutrients and for settlement stimulation by nutrients. To enable these measurements with relatively small volumes and numbers of released spores, we developed a computer‐assisted motion‐analysis assay for spore chemotaxis and verified the results with a more standard, capillary tube chemotaxis assay. The presence of a nutrient gradient did not influence the swimming behavior of E. siliculosus spores in the motion‐analysis assay, and likewise no chemotactic effect was measured in the capillary tube assay. Microplate settlement assays previously utilized with bacteria and invertebrates were adapted for use with algal spores. E. siliculosus spores settled at higher rates on a hydrophobic plastic surface than on surfaces with either positively or negatively charged hydrophilic coatings. Nutrient mixtures had no effect on the rate of spore settlement on hydrophobic surfaces.