PUCHI regulates very long chain fatty acid biosynthesis during lateral root and callus formation

© 2019 National Academy of Sciences. All rights reserved. Lateral root organogenesis plays an essential role in elaborating plant root system architecture. In Arabidopsis, the AP2 family transcription factor PUCHI controls cell proliferation in lateral root primordia. To identify potential targets of PUCHI, we analyzed a time course transcriptomic dataset of lateral root formation. We report that multiple genes coding for very long chain fatty acid (VLCFA) biosynthesis enzymes are induced during lateral root development in a PUCHI-dependent manner. Significantly, several mutants perturbed in VLCFA biosynthesis show similar lateral root developmental defects as puchi-1. Moreover, puchi-1 roots display the same disorganized callus formation phenotype as VLCFA biosynthesis-deficient mutants when grown on auxin-rich callus-inducing medium. Lipidomic profiling of puchi-1 roots revealed reduced VLCFA content compared with WT. We conclude that PUCHI-regulated VLCFA biosynthesis is part of a pathway controlling cell proliferation during lateral root and callus formation

Natural diversity in the carotene, tocochromanol and fatty acid composition of crude palm oil

International audienceCrude palm oil (CPO) is extracted from the mesocarp of oil palm (Elaeis guineensis) fruits. CPO is widely consumed in many African countries. Due to its high provitamin A carotenoid content, it is also widely used in programmes designed to prevent vitamin A deficiency. Elaeis guineensis occurs naturally across a wide geographical range in Africa. We investigated the carotene, tocochromanol (vitamin E) and fatty acid composition of a large set of genotypes representative of this genetic and geographic diversity. We found considerable intraspecific diversity in most lipid traits. Populations from Côte d'Ivoire were distinguished from other origins by their very low palmitate content and high tocochromanol content. Genotypes from Benin, Côte d'Ivoire and Nigeria were characterized by high carotene contents. Finally, hybrids of crosses between genotypes from Côte d'Ivoire and Nigeria produce CPO with exceptionally high provitamin A and vitamin E contents together with low palmitate content

The embryo and the endosperm contribute equally to argan seed oil yield but confer distinct lipid features to argan oil

International audienceIn the perspective of studying lipid biosynthesis in the argan seed, the anatomy, ploidy level and lipid composition of mature seed tissues were investigated using an experimental design including two locations in Algeria and four years of study. Using flow cytometry, we determined that mature argan seeds consist of two well-developed tissues, the embryo and the endosperm. The lipid content of the embryo was higher than that of the endosperm, but the dry weight of the endosperm was higher. Consequently, both tissues contribute equally to seed oil yield. Considerable differences in fatty acid composition were observed between the two tissues. In particular, the endosperm 18:2 percentage was twofold higher than that of the embryo. The tocopherol content of the endosperm was also markedly higher than that of the embryo. In contrast, the endosperm and the embryo had similar sterol and triterpene alcohol contents and compositions

Rôle écologique des diterpènes accumulés dans les graines de caféiers

Les caféiers produisent des graines albuminées qui accumulent de grandes quantités de métabolites secondaires, notamment des diterpènes (ca. 1-2% MS). Le cafestol et le kahweol sont les principaux diterpènes spécifiques des caféiers et ils sont stockés sous forme estérifiée à l'acide palmitique. Si leurs propriétés pharmacologiques ont été largement étudiées, leur rôle écologique est encore inconnu. Plusieurs études montrent l'implication de nombreux diterpènes dans la défense des plantes contre les bioagresseurs. Ainsi, nous avons testé l'activité des formes libres et estérifiées du cafestol sur la croissance d'un panel de bioagresseurs, comprenant six souches de champignons phytopathogènes et deux espèces de mouches des fruits. Le cafestol ralentit la croissance des champignons Colletotrichum gloeosporioides, Fusarium oxysporum, Fusarium proliferatum, Fusarium solani et Talaromyces stollii, dès 0,1mM. Il n'a pas d'effet sur Aspergillus niger. La consommation de cafestol par les larves de la mouche des fruits Bactrocera dorsalis entraîne un ralentissement de la pupation et une diminution du taux de pupation, de la masse des pupes et des mouches. La plupart de ces effets sont observés dès 1mM. Ce diterpène n'impacte pas le développement de la mouche Ceratitis capitata. Pour l'ensemble des organismes testés, aucun effet n'a été mesuré pour le palmitate de cafestol. Ces résultats suggèrent l'implication des diterpènes dans la défense de la graine in planta ou au sol. Pour déterminer si les diterpènes joueraient également un rôle dans la protection de la jeune plantule, nous avons étudié leur devenir au cours de son développement après la germination. La teneur et la composition en diterpènes des tissus de la graine (albumen et embryon) et de la plantule (racine, hypocotyle et cotylédon) ont été analysés par HPLC-DAD. Les quantités de cafestol et de kahweol diminuent dans l'albumen au cours de sa digestion et augmentent en parallèle dans tous les tissus de la plantule au cours de sa croissance. Ces résultats soutiennent l'hypothèse d'un transfert des diterpènes depuis l'albumen vers la plantule pour sa protection contre les bioagresseurs

Diterpenes of Coffea seeds show antifungal and anti-insect activities and are transferred from the endosperm to the seedling after germination

International audienceSpecies of the genus Coffea accumulate diterpenes of the ent-kaurane family in the endosperm of their seeds, of which cafestol and kahweol are the most abundant. The diterpenes are mainly stored in esterified form with fatty acids, mostly palmitate. In contrast to the numerous studies on their effects on human health and therapeutic applications, nothing was previously known about their biological and ecological role in planta. The antifungal and anti-insect activities of cafestol and cafestol palmitate were thus investigated in this study. Cafestol significantly affected the mycelial growth of five of the six phytopathogenic fungi tested. It also greatly reduced the percentage of pupation of larvae and the pupae and adult masses of one of the two fruit flies tested. By contrast, cafestol palmitate had no significant effect against any of the fungi and insects studied. Using confocal imaging and oil body isolation and analysis, we showed that diterpenes are localized in endosperm oil bodies, suggesting that esterification with fatty acids enables the accumulation of large amounts of diterpenes in a non-toxic form. Diterpene measurements in all organs of seedlings recovered from whole seed germination or embryos isolated from the endosperm showed that diterpenes are transferred from the endosperm to the cotyledons during seedling growth and then distributed to all organs, including the hypocotyl and the root. Collectively, our findings show that coffee diterpenes are broad-spectrum defence compounds that protect not only the seed on the mother plant and in the soil, but also the seedling after germination

Regulation of FUSCA3 Expression During Seed Development in Arabidopsis

International audienceFUSCA3 (FUS3) is a master regulator of seed development important in establishing and maintaining embryonic identity whose expression is tightly regulated at genetic and epigenetic levels. Despite this prominent role, the control of FUS3 expression remains poorly understood. Promoter and functional complementation analyses provided insight into the regulation of FUS3. W-boxes present in the promoter proximal to the start of transcription are recognized by WRKY type-1 factors which are necessary for the activation of FUS3 expression. The RY motif, the binding site of B3 factors, is important for the activation of FUS3 in the embryo proper but not in the suspensor. The loss of a negative regulatory sequence (NRS) leads to preferential expression of FUS3 in the vasculature of vegetative tissues. Since the NRS includes the RY motif, mechanisms of activation and repression target adjacent or overlapping regions. These findings discriminate the regulation of FUS3 from that of LEAFY COTYLEDON2 by the control exerted by WRKY factors and by the presence of the RY motif, yet also confirm conservation of certain regulatory elements, thereby implicating potential regulation by BASIC PENTACYSTEINE (BPC) factors and POLYCOMB REPRESSIVE COMPLEX2 (PRC2)