Morphological Characterization and Transcriptional Regulation of Corolla Closure in Ipomoea purpurea

Corolla closure protects pollen from high-temperature stress during pollen germination and fertilization in the ornamental plant morning glory (Ipomoea purpurea). However, the morphological nature of this process and the molecular events underpinning it remain largely unclear. Here, we examined the cellular and gene expression changes that occur during corolla closure in the I. purpurea. We divided the corolla closure process into eight stages (S0–S7) based on corolla morphology. During flower opening, bulliform cells appear papillate, with pigments in the adaxial epidermis of the corolla. These cells have distinct morphology from the smaller, flat cells in the abaxial epidermis in the corolla limb and intermediate of the corolla. During corolla closure, the bulliform cells of the adaxial epidermis severely collapse compared to cells on the abaxial side. Analysis of transparent tissue and cross sections revealed that acuminate veins in the corolla are composed of spiral vessels that begin to curve during corolla closure. When the acuminate veins were compromised, the corolla failed to close normally. We performed transcriptome analysis to obtain a time-course profile of gene expression during the process from the open corolla stage (S0) to semi-closure (S3). Genes that were upregulated from S0 to S1 were enriched in the polysaccharide degradation pathway, which positively regulates cell wall reorganization. Senescence-related transcription factor genes were expressed beginning at S1, leading to the activation of downstream autophagy-related genes at S2. Genes associated with peroxisomes and ubiquitin-mediated proteolysis were upregulated at S3 to enhance reactive oxygen species scavenging and protein degradation. Therefore, bulliform cells and acuminate veins play essential roles in corolla closure. Our findings provide a global understanding of the gene regulatory processes that occur during corolla closure in I. purpurea.

Anticancer Activity of Ipomoea purpurea Leaves Extracts in Monolayer and Three-Dimensional Cell Culture

Cancer is a leading cause of death and a vital health care challenge in the world. Hence, this work was conducted to determine the in vitro anticancer property and also the molecular mechanism of aqueous and organic extracts of Ipomoea purpurea leaves in three human cancer cell lines, including A-549 (human lung cancer), HepG-2 (human liver cancer), MDA-MB-231 (human breast cancer), and MCF-10A (breast normal cell line). In vitro cytotoxic potential of organic extracts, such as hexane, chloroform, ethyl-acetate, methanol, and aqueous extract was examined using a standard (3-(4,5-dimethylthiazole)-2,5-diphenyltetrazolium bromide) MTT method in both monolayer two-dimensional (2D) and spheroids multicellular three-dimensional (3D) cultures. The MTT assay data showed that methanol and chloroform extracts of I. purpurea leaves had the antiproliferative effect on lung and breast cancer cells with IC50 of 53.62 ± 0.07 and 124.5 ± 0.01 µg/mL, respectively. The results of further examinations, such as dual acridine orange/ethidium bromide, Annexin V-FITC/PI, and caspase-3 colorimetric assay, confirmed that methanol and chloroform extracts of I. purpurea as the most potent cytotoxic extracts might contain a variety of phytochemicals, promoting apoptosis in lung and breast cancer cells. The present research findings suggested that methanolic extract of I. purpurea leaves induced S-phase cell cycle arrest and intrinsic pathway of apoptosis in A-549 lung cancer cells. The study further showed that I. purpurea could be a helpful candidate for cancer treatment.

Nitrogen, phosphorus and potassium nutrition on ornamental Ipomoea purpurea growth

O estudo objetivou avaliar o efeito de nitrogênio, fósforo e potássio no crescimento de I. purpurea. As plantas foram fertilizadas semanalmente com 50 mL de solução nutritiva modificada de Hoagland & Amon (1950): Nitrogênio com 0; 0,0888; 0,201; 0,6003 ou 1,801 g L-1 de nitrato de amônio; Fósforo com 0; 2,1; 5,5; 10,3 ou 13,5 mL L-1 de ácido fosfórico e Potássio com 0; 0,3728; 1,1183; 1,8638 ou 2,2065 g L-1 de cloreto de potássio. I. purpurea apresentaram alta demanda por N, que resultou em aumento da área foliar. A maior concentração de N promoveu investimento preferencial nas áreas fotossintéticas, confirmado pela relação folha/raiz. I. purpurea é responsiva a fertilização com fósforo, principalmente para promover o crescimento de caule e raízes. I. purpurea não respondeu à fertilização com K. Os resultados do estudo recomendam a fertilização com 0,2001 g L-1 de nitrato de amônio e 5,5 ml L-1 de ácido fosfórico no cultivo de I. purpurea.

Asteraceae family: a review of its allelopathic potential and the case of Acmella oleracea and Sphagneticola trilobata

Asteraceae family is as an interesting target for researching natural alternatives for crop protection. Many species from this family grow as weeds, and some of them can influence the development of other species by the allelopathy phenomenon. This paper aimed to review the literature for the main genera and species of the Asteraceae family with allelopathic or phytotoxic potential, as well as the classes of secondary metabolites present in this family and responsible for such activity. Artemisia, Ambrosia, Bellis, Bidens, Helianthus and Tagetes were identified as the main genera with phytotoxic or allelopathic activity. Among the secondary metabolites from this family, terpenes, polyacetylenes, saponins, sesquiterpene lactones, phenolic acids and flavonoids were described as responsible for inhibiting the development of other species. In addition, the phytotoxic potential of Acmella oleracea and Sphagneticola trilobata against the weeds Calopogonium mucunoides. and Ipomoea purpurea was described for the first time. At 0.2 mg/mL, crude extract and fractions of A. oleracea inhibited above 60% of C. mucunoides root growth. Hydroalcoholic extract and fractions of S. trilobata, except hexane, significantly affected I. purpurea root growth, ranging from 38 ± 14% to 59 ± 8% of inhibitory effect at different concentrations (0.19 mg/mL to 1.13 mg/mL).

First report of the parasitic invasive weed field dodder (Cuscuta campestris) parasitizing the confamilial invasive weed common morning-glory (Ipomoea purpurea) in Shandong, China

Common morning-glory (Ipomoea purpurea (L.) Roth, Convolvulaceae), an annual herbaceous vine native to South America, was first recorded to be cultivated in China in 1890, and since then it has invaded all provinces of China. It was one of the 18 alien invasive species in China (MEE. 2014). As an invasive weed, it can readily invade dry lands, orchards, and nurseries and compete for sunlight by wrapping other plants. On 20 September 2019 and 18 July 2020, I. purpurea was found to be parasitized by a dodder species (also Convolvulaceae) in Lushan Mountain (36°21′N, 118°3′E, 569 m elevation), Shandong province, China (Fig. S1). Within and area of ca. 100 m2, dozens of individuals of common morning-glory were parasitized by the leafless stems of dodder. After removal of the haustrial connection of the dodder stem from the I. purpurea stem, brownish black lesions around uneven holes were visible on the I. purpurea stem, with broken haustoria clearly visible to our naked eye remaining in the I. purpurea stem (Fig. S1). Anatomical results showed that the haustoria of dodder penetrate I. purpurea stem and xylem elements connect the vascular systems of both the parasitic and host plant (Fig. S1). Based on morphological characteristics of stems, inflorescences, calyx, corolla, stamens, and capsules as described in Costea et al. (2006), this dodder was identified as Cuscuta campestris Yunck. (i.e., field dodder). Field dodder is readily distinguished from C. chinensis and C. australis in China by the capsules with persistent corollas enveloping 1/3 or less of its base and the spreading and inflexed corolla lobes with acute to acuminate apices. In order to further confirm the identity of the species, total genomic DNA was extracted and sequenced using genome-skimming method as described in Qu et al. (2019). An 831-bp region of 18S-ITS1-5.8S-ITS2-26S for the dodder studied was assembled, examined, and deposited in GenBank under accession number MN718805. The new sequence has 100% similarity with other available sequences of C. campestris (accession number: KT383104, KT383150, KY968857). Phylogenetic analysis also placed the new dodder accession with other accessions of C. campestris (Fig. S2a). In addition, the plastome sequence of the dodder studied was assembled (86,727 bp in length) and deposited in GenBank under accession number MN708214, and a BLAST analysis found that it was 99.98% similar to that of C. gronovii (accession number: AM711639). The plastome of C. gronovii was published by Funk et al. (2007). However, Costea et al. (2015) indicated that Funk et al. (2007) misidentified C. campestris as C. gronovii. Furthermore, our phylogenetic tree strongly supported the identification of the dodder studied as C. campestris (Fig. S2b). Therefore, the dodder on common morning-glory in Shandong province was finally identified as C. campestris according to morphological and molecular evidence. The specimen of C. campestris on I. purpurea was deposited at the herbarium of the College of Life Sciences, Shandong Normal University (voucher number: 092012B). Field dodder, the second most common dodder species in North America, is the most widespread Cuscuta weed in the world and has been found in Africa, Asia, Australia, Europe, and South America (Holm et al. 1997). To our knowledge, this is the first report of the parasitic invasive weed C. campestris parasitizing the invasive weed I. purpurea in Shandong of China. This is also the first report of Cuscuta species parasitizing confamilial Ipomoea species, which is especially noteworthy given that the genus Cuscuta is sister to the genus Ipomoea. This study provides a good model for exploring gene flow between species of closely related genera with different lifestyle. Another implication of this study is that customs and departments of inspection and quarantine need to quarantine the seeds or plants of both dodders and common morning-glories.

Variable inbreeding depression may explain associations between the mating system and herbicide resistance

Inbreeding depression is a central parameter underlying mating system variation in nature and one that can be altered by environmental stress. Although a variety of systems show that inbreeding depression tends to increase under stressful conditions, we have very little understanding across most organisms how the level of inbreeding depression may change as a result of adaptation to stressors. In this work we examined the potential that inbreeding depression varied among lineages of Ipomoea purpurea artificially evolved to exhibit divergent levels of herbicide resistance. We examined inbreeding depression in a variety of fitness-related traits in both the growth chamber and in the field. We paired our examination of inbreeding depression in fitness-related traits with an examination of gene expression changes associated with the level of herbicide resistance, breeding history (inbred or outcrossed), and the interaction of the breeding system and the level of herbicide resistance. We found that, while inbreeding depression was present across many of the traits, lineages artificially selected for increased herbicide resistance often showed no evidence of inbreeding depression in the presence of herbicide, and in fact, showed evidence of outbreeding depression in some traits compared to non-selected control lines and lineages selected for increased herbicide susceptibility. Further, at the transcriptome level, the resistant selection lines had differing patterns of gene expression according to breeding type (inbred vs outcrossed) compared to the control and susceptible selection lines. Our data together indicate that inbreeding depression may be lessened in populations that are adapting to regimes of strong selection.