Wan-Jean Hsu

PHOTOTROPISM IN PHYCOMYCES MUTANTS LACKING β-CAROTENE

Abstract. β‐carotene and riboflavin are considered as the major candidates for the photoreceptor for physiological responses to blue light in Phycomyces and a number of other organisms. Mutants of Phycomyces blocked in all six steps of the biosynthesis of β‐carotene from phytoene contain no detectable β‐carotene (less than 4 times 10‐5 of wild‐type amount) but exhibit phototropic responses identical to wild‐type. Moreover, wild‐type Phycomyces, while abundant in trans‐β‐carotene, contains no detectable cis‐β‐carotene, sometimes proposed as a photoreceptor candidate on the basis of the close similarity of the cis‐species absorption spectrum in the near UV region to many action spectra for blue‐light responses. These results indicate that β‐carotene cannot be the photoreceptor for phototropism in Phycomyces.

Structure--activity relationships of chemical inducers of carotenoid biosynthesis☆

Abstract Fifteen amines having a profound effect on carotenogenesis in Marsh seedless grapefruit are reported. The compounds fall into three series: Et2N(CH2)nMe (n = 4–8), Et2N(CH2)nPh (n = 1–5), and Et2NCH2CH2OC6H4R (R=H, p-Me, p-Et, p-iso-Pr, p-tert-Bu), There was up to an 11-fold increase in the total carotene content. Lycopene, not normally accumulated, became a major pigment. The inducing ability of the amines on carotenoid biosynthesis is correlated with the octanol-water partition coefficient. The mode of action appears to be similar to that of 2-(4-chlorophenylthio)triethylamine hydrochloride.

Effects of amines on the carotenogenesis in Blakeslea trispora

Abstract Six amines profoundly affected carotenogenesis in Blakeslea trispora . When cultures were treated with the amines, namely 4-[β-(diethylamino)-ethoxy]-benzaldehyde, 4-[β-(diethylamino)-ethoxy]-acetophenone hydrochloride, 4-β-(diethylamino)-ethoxy]-benzophenone hydrochloride, triethylamine hydrochloride, α-diethylaminopropiophenone hydrochloride and tributylamine hydrochloride, an increase in the lycopene accumulation was observed. The modes of action of these amines appear to be similar to that of 2-(4-chlorophenylthio)triethylamine hydrochloride (CPTA); however, they difrer in relative effectiveness.

Chemical induction of β-carotene biosynthesis

Abstract Marsh white seedless grapefruit were treated with the 2-diethylaminoethanol esters of the following acids: benzoic, phenylacetic, hydrocinnamic, 4-phenylbutyric, 5-phenylvaleric, valeric, hexanoic, heptanoic, octanoic, nonanoic, 5-chlorovaleric, cyclohexanecarboxylic, phenoxyacetic, p -chlorophenoxyacetic, 3-phenoxypropionic, cinnamic and p -chlorocinnamic. Several of these esters, in particular the hexanoate, 4-phenylbutyrate and cinnamate, caused the accumulation of large amounts of β-carotene. The effects of the hexanoate and of 2-phenoxytriethylamine, which causes only lycopene accumulation, were studied as functions of time. The hexanoate caused the rapid accumulation of lycopene during the first day. The amount of lycopene then began to decrease and that of β-carotene increased until, after 14 days, β-carotene was the major pigment. 2-Phenoxytriethylamine caused rapid lycopene accumulation during the first day and a slow steady increase afterwards. Thus, the mode of action of the β-carotene inducers may be similar to that of the lycopene inducers except that the former are probably rapidly hydrolysed by the esterase(s) in the flavedo, so that they no longer inhibit the cyclase(s), and β-carotene is accumulated at the expanse of lycopene.

Chemical bioregulation of carotenogenesis in phycomyces blakesleeanus

Abstract 2-(4-chlorophenylthio)Triethylamine (CPTA) and three N,N -diethylalkylamines affected carotenogenesis in Phycomyces blakesleeanus wild type NRRL 1555 and carA mutants C2, C3 and C152. The mode of action of the N,N -diethylalkylamines appears to be similar to that of CPTA, but differ in relative effectiveness. In all cases, carotenogenesis was stimulated and lycopene accumulated as the major pigment with concomitant increase of γ-carotene. N,N -Diethylbutylamine and N,N -diethylhexylamine seem to be more effective than CPTA in inducing carotenogenesis in Phycomyces wild type NRRL 1555 and carA mutants.

Carotenogenesis in Phycomyces

Abstract Time course studies of carotenoid production and of mycelial growth in liquid cultures of Phycomyces blakesleeanus wild type [NRRL 1555 (−)], red mutants C9, C10 and C13 and the heterokaryon C2 * C9 are reported. The ratios of the concentrations of lycopene, γ-carotene and β-carotene in the red mutant C13 and in the heterokaryon C2 * C9 during the growth periods were measured. In these strains the concentration of lycopene is close to its final value after 2 days of growth, at a time at which β-carotene is just beginning to be produced. It is suggested that the β-carotene produced late is possibly synthesized via β-zeacarotene.

CHEMICAL REGULATION OF CAROTENOID BIOSYNTHESIS

A large number of onium compounds regulate carotenoid biosynthesis in plant tissues. Some exert their action by inhibition of biosynthetic pathways. Conversely, others stimulate the biosynthetic pathways. Research efforts involved in the development of the latter compounds have generated a substantial amount of information relative to structure-activity relationships for bioregulation of carotenoid pigments in microorganisms and higher plants. Both the trans - and cis - biosynthetic pathways can be regulated. Compounds of the general formula (C 2 H 5 ) 2 N CH 2 C 2 R stimulate the production of trans -carotenoids whereas compounds of the type (C 2 H 5 ) 2 N R 1 R 2 regulate the biosynthesis of cis -carotenoids. The carotenoid pattern observed is determined essentially by the nature of the onium compounds employed.

Synthetic regulators of carotenoid biosynthesis in Citrus paradisi

Abstract The ability of 16 amines to induce carotenoid biosynthesis in Marsh seedless grapefruit is correlated with the octanol-water partition coefficient and the Hammett constants. The compounds fall into three series: p- RC 6 H 4 COOCH 2 CH 2 NEt 2 (R = H, NH 2 , CN, NO 2 , MeO, Me, tert -Bu, F, Cl, Br), p -RC 6 H 4 CH 2 NEt 2 (R = H, Me, NO 2 ), and RC 6 H 4 OCH 2 CH 2 NEt 2 (R = o -Me, m -Me, p -Me). Total carotene content increased up to 12-fold. Lycopene, not normally accumulated, became a major pigment. The benzoates caused up to a 24-fold increase in the β-carotene content. Except for the larger accumulation of cyclic carotenes, the mode of action of these amines appears to be similar to that of 2-(4-chlorophenylthio triethylamine hydrochloride.

Synthetic bioregulators of poly-cis carotenoid biosynthesis

Abstract Seventeen new bioregulators were synthesized and tested for their ability to induce the biosynthesis of poly- cis carotenes in the flavedo of Marsh white seedless grapefruit. The effects of these new bioregulators are the same as that of the previously reported dibenzylamines, but several of the new compounds are more effective and cause the accumulation of up to 162 μg/g dry wt of poly- cis carotenes in the flavedo as compared to the maximum of 74 μg/g dry wt observed previously. The compounds tested were substituted N -benzyl furfurylamines, N -benzyl, N -methyl furfurylamines and N -alkyl, N -methyl benzylamines. They demonstrate the ability of tertiary as well as secondary amines to stimulate the formation of poly-cis carotenes. The interaction of N -(4-bromobenzyl) furfurylamine, one of the more effective of the new compounds, with lycopene and β-carotene inducers is also reported.

Chemical induction of poly-cis carotenoid biosynthesis

Abstract A new class of synthetic bioregulators is reported which cause the accumulation of poly-cis carotenoids in the flavedo of Marsh white seedless grapefruit. The compounds tested were all secondary amines: dibenzylamine, substituted dibenzylamines (4-F; 4-Cl; 4-Br; 2-, 3-and 4-Me; 4-NO2; 4-CN; 4-Cl, 4′-Me; 4-Me, 4′-NO2), N-benzyl phenethylamine and N-benzyl 2-naphthalenemethylamine. The most effective, 4-chlorodibenzylamine, caused the accumulation of 74μgg/g dry wt of poly-cis carotenoids. Prolycopene was the predominant pigment but substantial amounts of proneurosporene, poly-cis-γ-carotenes and other cis carotenes were also present. The mode of action of these new bioregulators is probably gene derepression, the same as that of the lycopene inducers. However, the secondary amines probably derepress a recessive gene governing the biosynthesis of poly-cis carotenoids; whereas, the lycopene inducers derepress the dominant gene that gives rise to the normal all-trans carotenoids. The new compounds did not seem to inhibit the cyclase(s), as the lycopene inducers do.