Application of Optimal Combined Microfertilizers of Boron, Molybdenum, and Copper Improves Root Tuber Yield Trait and Photosynthetic Response Characteristics in Pseudostellaria heterophylla

In the actual cultivation process, blind fertilizer application was widespread, resulting in a serious decline in the yield of Pseudostellaria heterophylla. We used the 3414 fertilizer experiment design to study the effects of combined Boron (B), Molybdenum (Mo), and Copper (Cu) on the growth indexes, diurnal changes of photosynthesis, and rapid fluorescence induction dynamics in P. heterophylla. Our results show that the optimal combination of B, Mo, and Cu simultaneously promoted the growth of underground and aboveground parts, and significantly improved the quality of single root tuber and yield per unit area. The best combination was treatment 9 (T9 = B, 1 g/L; Mo, 0.08 g/L; Cu, 0.05 g/L), and resulted in a 35.1% increase in yield per unit area compared with the control group (T1). Although the optimal combined application of microfertilizers did not change the bimodal trend of diurnal variation of photosynthesis, it effectively increased the daily average, peak, and valley values of the photosynthetic rate by alleviating the nonstomatal limitation and the photosynthetic midday depression. Pseudostellaria heterophylla leaves showed greater photochemical activity and less photoinhibition of photosystem II in T9. Major effects were that it helped protect the activity of the oxygen-evolving complex to reduce the oxidative damage of chloroplasts and prevent the dissociation of thylakoid. The microfertilizer application also enhanced the electron receiving ability of the QB and plastoquinone (PQ) electronic pools, thereby increasing the ability of electron transfer from QA to QB. The number of reaction centers per unit area was promoted notably by the fertilization treatment.

Pseudosterins A–C, Three 1-Ethyl-3-formyl-β-carbolines from Pseudostellaria heterophylla and Their Cardioprotective Effects

Pseudostellaria heterophylla is used in China not only as a functional food but also as an herb to tonify the spleen, enhance immunity, and treat palpitation. Our previous investigation showed that a fraction enriched in glycosides obtained from the roots of P. heterophylla possessed pronounced protective effects on H9c2 cells against CoCl2-induced hypoxic injury. However, the active compounds responsible for the observed effects were still unknown. In the current investigation, pseudosterins A–C (1–3), three new alkaloids with a 1-ethyl-3-formyl-β-carboline skeleton, together with polydatin, have been isolated from the active fraction. Their structures were elucidated on the basis of spectroscopic analysis and quantum chemical calculations. The four compounds showed cardioprotective effects against sodium hydrosulfite-induced hypoxia-reoxygenation injury in H9c2 cells, with the three alkaloids being more potent. This is also the first report of alkaloids with a β-carboline skeleton isolated from P. heterophylla as cardioprotective agents.

Stimulatory Effect of Fe3O4 Nanoparticles on the Growth and Yield of Pseudostellaria heterophylla via Improved Photosynthetic Performance

Nanomaterials have recently been used as growth stimulants to promote the production of crops in saline-alkali through root application. However, if applied through leaves, little is known about the effect of Fe3O4 nanoparticles (NPs) on the root growth and yield, especially for medicinal crops. To fill this gap, a single factor experiment was conducted to explore the effects of Fe3O4 NPs on growth, yield, the dry matter distribution, chlorophyll content, photosynthetic characteristics, chlorophyll fluorescence parameters, and polysaccharide content of Pseudostellaria heterophylla by foliar spraying under field conditions. Fe3O4 NPs (20–50 mg·L–1) significantly promoted growth, the dry matter distribution of root and root tuber yield per unit area. Fe3O4 NPs enhanced net photosynthetic rate (Pn) by increasing chlorophyll content. And Fe3O4 NPs increased the daily mean and peak value of Pn, and alleviated the phenomenon of “midday depression” by improving nonstomatal limitation. Chlorophyll fluorescence parameters indicating that Fe3O4 NPs promoted the photochemical activity of PSII and alleviated photoinhibition by enhancing the photochemical use of excess excitation energy. Gray correlation analysis showed that Fe3O4 NPs enhanced the adaptability of P. heterophylla photosynthesis to high temperatures and strong light. Of note, Fe3O4 NPs enhanced the polysaccharide content of the root tuber. Phytotoxic effect was recorded at high NPs (100 mg·L–1) doses. Collectively, Fe3O4 NPs could promote performance of P. heterophylla by improving photosynthetic performance, enhancing its adaptability to the environment, and increasing the distribution ratio of photosynthates to the underground part.

First report of Arcopilus aureus causing leaf black spot disease of Pseudostellaria heterophylla in China

Pseudostellaria heterophylla (family Caryophyllaceae) is a perennial herbaceous plant. Its tuberous roots are highly valued in traditional Chinese medicine. It is mainly cultivated in a geo-authentic production zone located in the Guizhou, Anhui, Shandong, and Fujian provinces of China (Zhao et al. 2016). The herb is widely used for treating lung diseases and as a spleen tonic (Pang et al. 2011). A severe leaf black spot disease was observed on P. heterophylla in China, from 2018 to 2020. Plants displayed water-soaking symptoms in the early stage of infection, then the watery areas turned brown-red and a black mold appeared on the lesions. At a later stage, the leaf spots showed concentric rings surrounded by a yellow halo, and the initial infection site became dry and necrotic (Supplementary Figure S1). Nine infected plants were collected from three cultivation fields in Shibing County (N 27°4'21", E 108°8'0"), Guizhou province, on April 13th, 2019. The fungus was consistently isolated from symptomatic leaves on potato dextrose agar (PDA) medium according to the method described by Larran et al (2002). A total of 22 isolates were obtained, including 7 isolates of Arcopilus and 15 isolates of Trichoderma. The growth rates of isolate MJ2-2b on PDA and oatmeal agar (OA) medium were 3 to 5 mm/day at 25 °C (Supplementary Figure S2A and S2B). Mycelium of isolate MJ2-2b was dense, yellowish-brown on PDA, while it was sparse, bright-red on OA. Also, the mycelium secreted brownish-red pigment on both PDA and OA. Ascomata when mature were water drop and limoniform. Lateral hairs were brown, erect or flexuous, tapering towards the tips. Ascospores when mature were greyish-white to grey, limoniform, or fusiform to pyriform (Supplementary Figure S2C and S2D). Further, the beta-tubulin gene (Tub2) of the fungus was amplified by using primer pairs T1 and TUB4Rd as described by Wang et al (2016) and subjected to sequencing. NCBI nucleotide BLAST results showed that sequences from seven isolates had a 99.86% identity with A. aureus (strain ChL-C, GenBank accession No. MG889987.1) (Supplementary Figure S2F). Molecular phylogenetic analysis by maximum likelihood method using MEGA 7 confirmed that the fungal isolate clustered with A. aureus. Hence, the causal agent was identified as A. aureus based on morphological and molecular characteristics. The sequence was deposited in GenBank (accession No. MW531453). Pathogenicity tests were conducted on 15-day old tissue-cultured seedlings according to Ghanbary et al (2018) (Supplementary Figure S3). Leaves of 16 seedlings were inoculated with 1×1 mm 5-day-old PDA-grown mycelial plugsof the fungal isolate. The experiment was repeated 3 times. After 10 days, the inoculated leaves showed the same symptoms observed on plants in the field. The associated fungal pathogen was consistently re-isolated from the inoculated seedlings and identified by Tub2 gene sequencing. At present, there are no reports of A. aureus causing disease of plants. To the best of our knowledge, this is the first report of leaf black spot disease on P. heterophylla caused by A. aureus in China.

Integrated Analyses of miRNAome and Transcriptome Reveal The Function of miRNAs in Morphogenesis of Organs and Defense of Endophytes in Pseudostellaria Heterophylla

Background: miRNAs play a crucial role in plant development and growth by inhibiting the function of targeted gene mRNAs at the post transcription level. However, none miRNAs in Pseudostellaria heterophylla has been reported and their function in morphogenesis of organs and continuous cropping obstacles is still unclear. Results: A total of 163 conserved miRNAs (belonging to 66 families) and 303 level miRNAs were identified and some of them showed specifically up or down regulated expression in different tissues. Further, numbers of unigenes involved in Plant-pathogen interaction and MAPK signaling pathway-plant was targeted by miRNAs from P. heterophylla by using GO and KEGG analysis. Significant negative correlation between expression profiles of 30 miRNAs and their targets gene (37 unigenes) were observed. Further, a large number of genes involving with signal transduction of auxin, zeatin, abscisic acid and jasmonic acid were targeted by identified miRNAs in P. heterophylla. A predicated target gene of a conserved and novel miRNA was validated by 5′RLM-RACE, respectively. A large number of mRNA from four kinds of endophytes was targeted by miRNAs of P. heterophylla, and most genes were targeted by miR414. Conclusion: We report a population of P. heterophylla miRNAs from four different vegetative organs by high throughput sequencing, and analyzed combining with the constructed transcriptome. These results may help to explain the function of miRNA in morphogenesis of organs and defense of endophytes in P. heterophylla, and provide theoretical basis for breeding and genetic improvement of P. heterophylla.