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The biosynthesis pathway to diadinoxanthin and fucoxanthin was elucidated in Phaeodactylum tricornutum by a combined approach involving metabolite analysis identification of gene function. For the initial steps leading to β-carotene, putative genes were selected from the genomic database and the function of several of them identified by genetic pathway complementation in Escherichia coli. They included genes encoding a phytoene synthase, a phytoene desaturase, a ζ-carotene desaturase, and a lycopene β-cyclase. Intermediates of the pathway beyond β-carotene, present in trace amounts, were separated by TLC and identified as violaxanthin and neoxanthin in the enriched fraction. Neoxanthin is a branching point for the synthesis of both diadinoxanthin and fucoxanthin and the mechanisms for their formation were proposed. A single isomerization of one of the allenic double bounds in neoxanthin yields diadinoxanhin. Two reactions, hydroxylation at C8 in combination with a keto-enol tautomerization and acetylation of the 3′-HO group results in the formation of fucoxanthin.
The existence of complex clauses in the Amazonian language Pirahã has been controversially debated. We present a novel analysis of field data demonstrating the existence of complex clauses in Pirahã. The data concern the tone of the morpheme 'sai' and stem from a field experiment where a second language speaker of Pirahã presented sentences and Pirahã speakers were asked to correct them saying the correct sentence alound. The experimental items contained the morpheme 'sai' in two different clausal environments: a nominalizer and a conditional environment according to Everett's 1986 description. Our phonetic analysis shows an effect clausal clausal environment on the pitch of 'sai'. The native Pirahã speakers pronounced conditional 'sai' with lower pitch than nominalizer 'sai'. We show furthermore that the experimenters pitch on 'sai' shows the opposite pattern from that of the native Pirahã speakers and hence the Pirahã's pitch could not just have been copied. The effect of the clausal environment on the tone of 'sai' can be explained by a complex clause analysis of Pirahã, while existing alternative proposals do not explain the difference.