Integrated Metabolomic and Transcriptomic Analysis of the Anthocyanin and Proanthocyanin Regulatory Networks in Red Walnut Natural Hybrid Progeny Leaves

BackgroundWalnuts are one of the most important dry fruit crops worldwide, typically exhibiting green leaves and yellow–brown or gray–yellow seed coats. A specific walnut type, red walnut ‘RW-1’, with red leaves and seed coats was selected as the plant material because of its higher anthocyanin and proanthocyanin (PA) contents. Anthocyanins and PAs coprise important secondary defense methods for plants to respond to biotic and abiotic stresses. However, few studies have focused on the molecular mechanism of anthocyanin biosynthesis in walnuts.ResultsFrom the results of widely targeted metabolome and anthocyanidin detection analysis, 395 substances, including 4 PAs and 26 anthocyanins, were identified from the red-leaf walnuts of RW-1 natural hybrid progenies (SR) and the green-leaf walnuts of RW-1 natural hybrid progenies (SG). Among these, all anthocyanin types in SR were significantly upregulated compared with SG. Additionally, delphinidin 3-O-galactoside, cyanidin 3-O-galactoside, delphinidin 3-O-glucoside and cyanidin 3-O-glucoside were identified as the primary components of anthocyanidins because of their higher contents. Nine anthocyanidins, malvidin 3-O-galactoside, malvidin 3-O-arabinoside, cyanidin 3-O-(6-O-malonyl-beta-D-glucoside), delphinidin 3-O-glucoside, delphinidin 3,5-O-diglucoside (Delphin), peonidin 3-O-(6-O-malonyl-beta-D-glucoside), petunidin 3-O-(6-O-malonyl-beta-D-glucoside), petunidin 3-O-arabinoside and pelargonidin 3-O-(6-O-malonyl-beta-D-glucoside), were detected only in the SR walnuts. For PAs, proanthocyanin C1 was upregulated in SR compared with SG, while proanthocyanin B1 and proanthocyanin B3 were upregulated in SR-1 and SR-3 but downregulated in SR-2 compared with the controls. Furthermore, transcriptome analysis demonstrated that the expression of structural genes (C4H, F3H, F3’5’H, UFGTs, LAR and ANR), four MYBs and six WD40s in the anthocyanin and PA biosynthetic pathways were significantly higher in the SR walnut.ConclusionsOur results provide valuable information on anthocyanin and PA metabolites and candidate genes in anthocyanin and PA biosynthesis, which provides new insights into anthocyanin and PA biosynthesis in walnuts.

Catasetum × sheyllae (Orchidaceae: Catasetinae), a new natural hybrid from Brazilian Amazon

Natural hybridization has often been recorded within certain genera of orchids, one of them is Catasetum. During a field study in a forest de igapó in Brazilian Amazon, a new natural hybrid was found, it is here described as Catasetum × sheyllae. Its morphological features, mainly the structures of the lip, are intermediate between those of its putative parent species, C. boyi and C. garnettianum, both observed in sympatry.

Floral Trait and Mycorrhizal Similarity between an Endangered Orchid and Its Natural Hybrid

Hybridization can often lead to the formation of novel taxa which can have traits that resemble either or both parental species. Determining the similarity of hybrid traits to parental taxa is particularly important in plant conservation, as hybrids that form between rare and common taxa may more closely resemble a rare parental species, thereby putting the rare parental taxon at further risk of extinction via increased backcrossing and introgression. We investigated the floral (morphological and chemical) traits and orchid mycorrhizal (OrM) fungal associations of the endangered orchid Orchis patens, its more common sister species O. provincialis, and their natural hybrid O. × fallax in natural sympatric populations. We found that both morphological and chemical floral traits of O. × fallax are shared by the parents but are more similar to O. patens than O. provincialis. OrM fungi were shared among all three taxa, indicating that the availability of OrM fungi should not represent a barrier to establishment of individuals of any of these taxa. These results suggest that O. × fallax may be able to expand its distribution within a similar niche to O. patens. This highlights the importance of quantifying differences between hybrids and parental taxon in species conservation planning.

Integrated metabolomic and transcriptomic analysis of the anthocyanin regulatory networks in red walnut

Background Walnut is one of the most important dry fruit crops worldwide, typically green leaves and yellow-brown or gray-yellow seed coats. A specific walnut type, red walnut ‘RW-1’ with red leaves and seed coats was selected as plant material because of higher anthocyanins contents. Anthocyanins are important colorants with strong antioxidant activity, especially, benefic for human health. However, few studies focused on the molecular mechanism of anthocyanin biosynthesis in walnut. Results From the results of Widely Targeted Metabolome and anthocyanidin detection analysis, 395 substances, including 4 procyanidins and 26 anthocyanins, were identified from the red-leaf walnuts of RW-1 natural hybrid progenies (SR) and the green-leaf walnuts of RW-1 natural hybrid progenies (SG). Among these, all the anthocyanins in SR were significantly up-accumulated comparing with SG. Also, delphinidin 3-O-galactoside, cyanidin 3-O-galactoside, delphinidin 3-O-glucoside and cyanidin 3-O-glucoside were identified to the primary components of anthocyanidins because of the higher contents. It was noted that 9 anthocyanins including malvidin 3-O-galactoside, malvidin 3-O-arabinoside, cyanidin 3-O-(6-O-malonyl-beta-D-glucoside), delphinidin 3-O-glucoside, delphinidin 3,5-O-diglucoside (Delphin), peonidin 3-O-(6-O-malonyl-beta-D-glucoside), petunidin 3-O-(6-O-malonyl-beta-D-glucoside), petunidin 3-O-arabinoside and pelargonidin 3-O-(6-O-malonyl-beta-D-glucoside) were detected only in SR walnut. Furthermore, transcriptome analysis demonstrated that the expression of structural genes (C4H, F3H, F3’5’H and UFGTs), and four MYBs in anthocyanin biosynthetic pathway were significantly higher in SR walnut. Conclusions We identified the color formation of SR leaves is due to the accumulation of anthocyanins. And our results obtained the valuable information on the anthocyanin metabolites and candidate genes in anthocyanin biosynthesis, which provided new insights into the anthocyanin biosynthesis in walnuts.

Calanthe × yarlungzangboensis, a new natural hybrid in genus Calanthe (Orchidaceae) from China

Calanthe × yarlungzangboensis P. P. Wu & Z. Wang, a new natural hybrid was described and illustrated from Xizang, China. Calanthe griffithii and C. tricarinata were considered as putative parentage by morphological traits and molecular data from nrITS and two plastid DNA (rbcL and matK). Calanthe × yarlungzangboensis is easily distinguished from its parentage by mid-lobe with three tuberculatus lamellae. The new hybrid grows in subalpine evergreen coniferous forest dominated by Tsuga dumosa in the eastern Himalayas with elevation about 2500m.