Pigment and Fatty Acid Production under Different Light Qualities in the Diatom Phaeodactylum tricornutum

Diatoms are microscopic biorefineries producing value-added molecules, including unique pigments, triglycerides (TAGs) and long-chain polyunsaturated fatty acids (LC-PUFAs), with potential implications in aquaculture feeding and the food or biofuel industries. These molecules are utilized in vivo for energy harvesting from sunlight to drive photosynthesis and as photosynthetic storage products, respectively. In the present paper, we evaluate the effect of narrow-band spectral illumination on carotenoid, LC-PUFAs and TAG contents in the model diatom Phaeodactylum tricornutum. Shorter wavelengths in the blue spectral range resulted in higher production of total fatty acids, namely saturated TAGs. Longer wavelengths in the red spectral range increased the cell’s content in Hexadecatrienoic acid (HTA) and Eicosapentaenoic acid (EPA). Red wavelengths induced higher production of photoprotective carotenoids, namely fucoxanthin. In combination, the results demonstrate how diatom value-added molecule production can be modulated by spectral light control during the growth. How diatoms could use such mechanisms to regulate efficient light absorption and cell buoyancy in the open ocean is discussed.

Discrimination of Chuanminshen violaceum Sheh et Shen from different regions based on fatty acid profiles of roots and leaves

Objectives The purpose of this paper was to construct a reliable methodology to discriminate the geographical origins of Chuanminshen violaceum Sheh et Shan planted in different regions in Sichuan, China. Materials and methods Fatty acid profiles of roots and leaves of C. violaceum planted in various regions of Sichuan Province in China, namely Guangyuan (GY), Langzhong (LZ), Jintang (JT), Bazhong (BZ), and Shuangling (SL), were determined using GC-MS followed by multivariate statistical analyses, including orthogonal partial least-squares discriminant analysis and hierarchical clustering analysis. Results Leaves of C. violaceum showed the highest contents of hexadecatrienoic acid (3.21 g/kg), linoleic acid (6.62 g/kg), and α-linolenic acid (7.24 g/kg), which were all higher than those contained in roots. Chuanminshen violaceum samples collected from LZ, JT, and GY could be clearly distinguished based on fatty acid profiles of leaves and those collected from LZ, GY, and BZ could be clearly distinguished based on fatty acid profiles of roots. Conclusions Chemometric method is used as a potential approach for analyses of fatty acid profiles of roots and leaves to control the quality of C. violaceum and their powered products.

The glycosyltransferase UGT76E1 significantly contributes to 12-O-glucopyranosyl-jasmonic acid formation in wounded Arabidopsis thaliana leaves

Jasmonoyl-isoleucine (JA-Ile) is a phytohormone that orchestrates plant defenses in response to wounding, feeding insects, or necrotrophic pathogens. JA-Ile metabolism has been studied intensively, but its catabolism as a potentially important mechanism for the regulation of JA-Ile–mediated signaling is not well-understood. Especially the enzyme(s) responsible for specifically glycosylating 12-hydroxy-jasmonic acid (12-OH-JA) and thereby producing 12-O-glucopyranosyl-jasmonic acid (12-O-Glc-JA) is still elusive. Here, we used co-expression analyses of available Arabidopsis thaliana transcriptomic data, identifying four UDP-dependent glycosyltransferase (UGT) genes as wound-induced and 12-OH-JA–related, namely, UGT76E1, UGT76E2, UGT76E11, and UGT76E12. We heterologously expressed and purified the corresponding proteins to determine their individual substrate specificities and kinetic parameters. We then used an ex vivo metabolite-fingerprinting approach to investigate these proteins in conditions as close as possible to their natural environment, with an emphasis on greatly extending the range of potential substrates. As expected, we found that UGT76E1 and UGT76E2 are 12-OH-JA-UGTs, with UGT76E1 contributing a major in vivo UGT activity, as deduced from Arabidopsis mutants with abolished or increased UGT gene expression. In contrast, recombinant UGT76E11 acted on an unidentified compound and also glycosylated two other oxylipins, 11-hydroxy-7,9,13-hexadecatrienoic acid (11-HHT) and 13-hydroxy-9,11,15-octadecatrienoic acid (13-HOT), which were also accepted by recombinant UGT76E1, UGT76E2, and UGT76E12 enzymes. UGT76E12 glycosylated 12-OH-JA only to a low extent, but also accepted an artificial hydroxylated fatty acid and low amounts of kaempferol. In conclusion, our findings have elucidated the missing step in the wound-induced synthesis of 12-O-glucopyranosyl-jasmonic acid in A. thaliana.