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Key Message: Through the histological, physiological, and transcriptome-level identification of the abscission zone of Pennisetum alopecuroides 'Liqiu', we explored the structure and the genes related to seed shattering, ultimately revealing the regulatory network of seed shattering in P. alopecuroides. Pennisetum alopecuroides is one of the most representative ornamental grass species of Pennisetum genus. It has unique inflorescence, elegant appearance, and strong stress tolerance. However, the shattering of seeds not only reduces the ornamental effect, but also hinders the seed production. In order to understand the potential mechanisms of seed shattering in P. alopecuroides, we conducted morphological, histological, physiological, and transcriptomic analyses on P. alopecuroides cv. 'Liqiu'. According to histological findings, the seed shattering of 'Liqiu' was determined by the abscission zone at the base of the pedicel. Correlation analysis showed that seed shattering was significantly correlated with cellulase, lignin, auxin, gibberellin, cytokinin and jasmonic acid. Through a combination of histological and physiological analyses, we observed the accumulation of cellulase and lignin during 'Liqiu' seed abscission. We used PacBio full-length transcriptome sequencing (SMRT) combined with next-generation sequencing (NGS) transcriptome technology to improve the transcriptome data of 'Liqiu'. Transcriptomics further identified many differential genes involved in cellulase, lignin and plant hormone-related pathways. This study will provide new insights into the research on the shattering mechanism of P. alopecuroides., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Key Message: Combination analysis of single-molecule long-read and Illumina sequencing provide full-length transcriptome information and shed new light on the anthocyanin accumulation mechanism of Pennisetum setaceum cv. 'Rubrum'. Pennisetum setaceum cv. 'Rubrum' is an ornamental grass with purple leaves widely used in landscaping. However, the current next-generation sequencing (NGS) transcriptome information of this species is not satisfactory due to the difficulties in obtaining full-length transcripts. Furthermore, the molecular mechanisms of anthocyanin accumulation in P. setaceum have not been thoroughly studied. In this study, we used PacBio full-length transcriptome sequencing (SMRT) combined with NGS technology to build and improve the transcriptomic datasets and reveal the molecular mechanism of anthocyanin accumulation in P. setaceum cv. 'Rubrum'. Therefore, 280,413 full-length non-chimeric reads sequences were obtained using the SMRT technology. We obtained 97,450 high-quality non-redundant transcripts and identified 5352 alternative splicing events. In addition, 93,066 open reading frames (ORFs), including 57,457 full ORFs and 2910 long non-coding RNA (lncRNAs) were screened out. Furthermore, 10,795 differentially expressed genes were identified using NGS. We also explored key genes, synthesis pathways, and detected lncRNA involved in anthocyanin accumulation, providing new insights into anthocyanin accumulation in P. setaceum cv. 'Rubrum'. To our best knowledge, we provided the full-length transcriptome information of P. setaceum cv. 'Rubrum' for the first time. The results of this study will provide baseline information for gene function studies and pave the way for future P. setaceum cv. 'Rubrum' breeding projects., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

Pennisetum grasses (P. purpureum Schumach. 'Purple', P. alopecuroides (L.) Spreng. 'Liren' and P. alopecuroides (L.) Spreng. 'Changsui'), and a cadmium (Cd) hyperaccumulator (Thlaspi caerulescens J.Presl & C.Presl), were grown in soil with four Cd addition levels of 0, 2, 20 and 200 mg/kg. Toxicity symptoms were not observed although growth of all plants decreased as Cd addition increased. Shoot bioconcentration factor (BCFS), the translocation factor (TF) and shoot accumulation of Cd for most plants first increased and then declined as Cd concentrations increased. In contrast, the root bioconcentration factor (BCFR) for T. caerulescens declined and root Cd accumulation for T. caerulescens and two P. alopecuroides cultivars increased consistently as Cd levels increased. P. purpureum had the largest biomass with shoot Cd accumulation similar to that of T. caerulescens, despite lower foliar Cd concentration. Although shoot Cd concentrations of two P. alopecuroides cultivars were lower than for P. purpureum, root Cd concentrations were greater. P. purpureum had Cd BCFS and TF (> 1) at 2- and 20-mg/kg Cd addition treatments, similar to T. caerulescens. P. alopecuroides cultivars had Cd BCFR (> 1) and TF (< 1) at all Cd levels. Roots did not affect rhizosphere pH. However, concentrations of acid extractable Cd in rhizosphere soil were lower than those of corresponding non-rhizosphere soil at all Cd levels for T. caerulescens and P. purpureum; T. caerulescens and P. purpureum did not affect less bioavailable Cd fractions. Concentrations of acid extractable Cd in the rhizosphere of the P. alopecuroides cultivars were not reduced at any Cd level. Differences in Cd accumulation among the three Pennisetum grasses were mainly attributable to root biomass and Cd TFs rather than rhizosphere Cd mobility., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The surface characterization and electrostatic property of Hybrid Pennisetum (HP) after alkaline sulfite pretreatment were explored for enhanced enzymatic hydrolysability. The O/C ratio in HP increased from 0.34 to 0.60, and C1 concentration decreased from 62.5% to 31.6%, indicating that alkaline sulfite pretreatment caused poorer lignin but richer carbohydrate on HP surface. Zeta potential and sulfur element analysis indicated that more enzymes would preferably adsorb on the carbohydrate surface of alkaline sulfite pretreated HP because the lignin was sulfonated, which facilitated the decrease of non-productive adsorption. Glucose yield of alkaline sulfite pretreated HP reached to 100% by synergistic action of cellulase and xylanase in the hydrolysis, which was significantly higher than that of NaOH pretreated, and the concentration of glucose released was 1.52times higher. The results suggested that alkaline sulfite pretreatment had potential for improving the HP hydrolysability, and the surface characterization and electrostatic property facilitated the enzymatic digestibility., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The effects of aqueous ammonia pretreatment on structural properties and hydrolysabilities of Chinese Pennisetum and Hybrid Pennisetum were investigated. Aqueous ammonia pretreatment increased cellulose crystallinities and hydrolysabilities of Chinese Pennisetum and Hybrid Pennisetum. Compared with Chinese Pennisetum, Hybrid Pennisetum showed better enzymatic digestibility. Xylanase supplementation was more effective than the increase of cellulase loadings in the hydrolysis of aqueous ammonia pretreated Chinese Pennisetum and Hybrid Pennisetum. After supplementation of 2mg of xylanase/g dry matter to 5 FPU of cellulases/g dry matter, the hydrolysis yields of cellulose of aqueous ammonia pretreated Chinese Pennisetum and Hybrid Pennisetum were 92.3-95.4%, and the hydrolysis yields of xylan were 86.9-94.2%. High hydrolysability and low dosage of enzyme loadings together with the advantages of high yield and widely distribution demonstrated the potential of Chinese Pennisetum and Hybrid Pennisetum for the production of platform sugars., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

So far no successful artificial hybridizations among ornamental grasses in the Pennisetum Rich. (Poaceae) genus that are widely applied in landscape design have been reported because of unclear genetic backgrounds and uncertain evolutionary and genetic relationships among one another, severely restricting the number of ornamental cultivars and their gardening utility. The present study aims to reveal genetic backgrounds and relationships for nine Pennisetum ornamental grasses via karyotype diversity analysis; discuss the morphological classification system proposed in previous studies on morphological, chromosomal and genomic levels; and verify the chromosomal evolution of Pennisetum genus using the combined karyotypic and genomic data. Our results indicated that (1) traditional morphological classification system of Pennisetum genus is reasonable, both from the morphological and cytological points of view; (2) hybridization among Pennisetum alopecuroides , P. alopecuroides ‘Little Bunny’, P. alopecuroides ‘Moudry’ and P. orientale may be easier to obtain a hit; (3) chromosomes with lower basic chromosome number are more asymmetry than those chromosomes with higher basic chromosome number, and taxa with different basic chromosome numbers may have experienced different way of speciation; and (4) chromosomal evolution in Pennisetum genus progressed from a symmetrical to an asymmetrical order in the course of evolution; and the structure of the genome of Pennisetum species involved in the reduction of chromosome number and an increase in their sizes and DNA contents. The present study guides the breeding programs and genome projects of Pennisetum ornamental grasses practically, and provides references for the evolutionary studies on Pennisetum genus theoretically. [ABSTRACT FROM AUTHOR]