Comparative transcriptome analysis of Lupinus polyphyllus Lindl. provides a rich molecular resource for research on coloration mechanism

Lupinus polyphyllus is rich in color, making it a well-known horticultural ornamental plant. However, little is known about the genes related to anthocyanin and carotenoid biosynthesis in L. polyphyllus. In this study, transcriptome sequencing was performed on eight different colors of L. polyphyllus. A total of 1.13 billion clean reads were obtained and assembled into 89,124 unigenes, which were then aligned with six databases, resulting in the identification of 54,823 annotated unigenes. Among these unigenes, 76 and 101 were involved in the biosynthetic pathway of carotenoids and anthocyanins, respectively. In addition, 505 transcription factors were revealed, which belonged to the MYB, R2R3-MYB, NAC, bHLH, and WD40 families. A total of 6,700 differentially expressed genes (DEGs) were obtained by comparative transcriptome analysis. Among them, 17 candidate unigenes (four carotenoid genes, seven anthocyanin genes, and six TFs) were specifically up-regulated for one or more colors of L. polyphyllus. Eight representative candidate unigenes were analyzed by qRT-PCR. The findings enrich the transcriptome database of lupine, and provide a rich molecular resource for research on the coloration mechanism of L. polyphyllus.

Viability of Wildflower Seeds After Mesophilic Anaerobic Digestion in Lab-Scale Biogas Reactors

The use of wildflower species as biogas feedstock carries the risk that their seeds survive anaerobic digestion (AD) and cause weed problems if spread with the digestate. Risk factors for seed survival in AD include low temperature, short exposure and hardseededness (HS). However, it is not possible to predict how AD will affect seed viability of previously unstudied species. In laboratory-scale reactors, we exposed seeds of eight species from a mixture of flowering wild plants intended as biogas feedstock and three reference species to AD at two mesophilic temperatures. Half of the species were HS, the other was non-HS (NHS). Viability was determined using a combination of tetrazolium and germination tests. Viability and germinability were modeled as functions of exposure time using a dose-response approach. Responses to AD varied considerably among species, and none of the considered influencing factors (time, temperature, HS) had a consistent effect. Seed lots of a species differed in inactivation times and seed-killing efficacy. The HS species Melilotus officinalis, Melilotus albus, and Malva sylvestris were particularly AD-resistant. They were the only ones that exhibited biphasic viability curves and tended to survive and germinate more at 42°C than at 35°C. Viability of the remaining species declined in a sigmoidal curve. Most NHS species were inactivated within a few days (Cichorium intybus, Daucus carota, Echium vulgare, and Verbascum thapsus), while HS species survived longer (Malva alcea). AD stimulated germination in the HS species A. theophrasti and its AD-resistance overlapped with that of the most resistant NHS species, C. album and tomato. In all seed lots, germinability was lost faster than viability, implying that mainly dormant seeds survived. After the maximum exposure time of 36 days, seeds of HS species and Chenopodium album were still viable. We concluded that viability responses to mesophilic AD were determined by the interplay of AD-conditions and species- and seed-lot-specific traits, of which HS was an important but only one factor. For the use of wildflowers as biogas feedstock, we recommended long retention times and special care with regard to HS species.