Gene-targeted molecular phylogeny,phytochemical profiling,and antioxidant activity of nine species belonging to family Cactaceae

Cactaceae plant family comprises over 130 genera and 2000 species of succulent flowering plants. The genera Mammillaria and Notocactus (Parodia), which have medicinal and nutritional applications as well as aesthetic appeal, are considered to be among the major genera of the family. Several species of both genera show morphological and chemical similarities and diversities according to environmental conditions and genotypes. Here, we assessed the genetic relationships of nine species belonging to two major genera Mammillaria and Notocactus under the family Cactaceae, using two modern gene-targeting marker techniques, the Start Codon Targeted (SCoT) Polymorphism and the Conserved DNA-Derived Polymorphism (CDDP). Besides, we screened the various phytochemicals and evaluated the antioxidant activities of the nine species of cacti. Five out of the 10 SCoT and eight CDDP primers used to screen genetic variations within the nine species yielded species-specific reproducible bands. The entire 156 loci were detected, of which 107 were polymorphic, 26 were monomorphic, and 23 were unique loci. The nine species were categorized into two groups based on the dendrogram and similarity matrix. Phytochemical profiling revealed that sterols, triterpenes, flavonoids, and tannins were found in all the tested species. Additionally, two Notocactus species (N. shlosserii and N. roseoluteus) and one Mammillaria species (M. spinosissima) revealed a considerable antioxidant activity. Our results demonstrated that gene-targeting marker techniques were highly powerful tools for the classification and characterization of the nine investigated species, despite displaying high similarities at both morphological and phytochemical levels.     

Influences of the genetic neighborhood on ramet reproductive success in a clonal desert cactus

Clonal structure in clonal plants can affect sexual reproduction. Individual ramets can decrease reproduction if their neighbors are ramets of the same genet due to inbreeding depression or self-incompatibility. We assessed ramet reproductive success in the partial self-incompatible Ferocactus robustus (Cactaceae) as a function of floral display size in focal ramets and floral display size and clonal structure of their reproductive neighborhoods. Ramets were labeled, sized in number of stems, mapped and genetically identified through RAPD markers in one population. A pollen dispersal area of 15-m radius was established for each ramet to determine the clonal diversity in the neighborhoods. Flower production and fruit set were counted on a monthly basis during one reproductive season as a surrogate of ramet fitness. We expected a decrease in individual ramet reproductive success as a function of the number of reproductive ramets of the same genet in the neighborhood. A total of 272 sampled ramets revealed 116 multilocus genotypes, showing high clonal diversity in the population (G/N = 0.43, D = 0.98). Clonal diversity of neighborhoods ranged from 0.06 to 1 and fruit set varied from 0 to 76.9%. Individual ramet reproductive success was influenced by (1) mate availability, (2) floral display size of a genet within the reproductive neighborhood, and (3) the proportion of distinguishable genotypes. Floral display size of genets and ramets coupled with the genetic diversity within the reproductive neighborhood determines the low sexual reproduction in F. robustus.     

Bat and hummingbird pollination of an AUTOTETRAPLOID COLUMNAR CACTUS,Weberbauerocereus weberbaueri (Cactaceae)

I present data on flower morphology, pollination, breeding system, and genetic diversity of the columnar cactus Weber-bauerocereus weberbaueri at 2500 m elevation in southwestern Peru. Weberbauerocereus weberbaueri is a self-compatible columnar cactus that is visited and pollinated by one species of rare endemic bat, Platalina genovensium, and two species of hummingbirds, Patagona gigas and Rhodopis vesper. W. weberbaueri exhibits pronounced interplant variation in floral color and size, and flowers exhibit traits corresponding to both bat and hummingbird pollination syndromes. Starch-gel electrophoresis of flower bud tissue indicated that W. weberbaueri is an autotetraploid and that genetic diversity (Hep = 0.257) of the study population was high relative to diploid plants but similar to other tetraploid species. Initial fruit set from pollinator exclusion experiments conducted in 1991 and 1993, at the onset of and after a drought associated with the El Niño event of 1991–1992, revealed that bats were the most important pollinators in 1991, but that hummingbirds and diurnal insects were most important in 1993. In both years, however, autogamy and lepidopteran larval infestation of fruits reduced differences in mature fruit production among pollinator exclusion treatments so that differences in mature fruit set were not statistically significant. Reduced bat pollination in 1993 is attributed to the reduced abundance of bats at the study site during a drought caused by El Niño. I hypothesize that interaction among several factors, including tetraploidy, autogamy, larval infestation of developing fruits, and variation in pollinator abundance, may not result in strong selection for a bat vs. hummingbird floral morph, thus allowing the persistence of floral variation in this cactus.     

Extreme population subdivision or cryptic speciation in the cactus Pilosocereus jauruensis? A taxonomic challenge posed by a naturally fragmented system

In allopatric systems, where gene flow is highly constrained, the distinction between intraspecific differentiation and speciation is a challenging task. Pilosocereus jauruensis is a columnar cactus restricted to patchy dry habitats of Pantanal, Cerrado, and Chaco biomes in south-western Brazil and neighbouring countries. This species was recently reinstated after having been synonymized with P. machriisi, now including P. paraguayensis, P. saudadensis, and P. densivillosus as its synonyms. These taxa have been placed within the informal Aurisetus group. The present study aimed to investigate the genetic structure of P. jauruensis in order to identify possible distinct evolutionary lineages, and to support further refinement of the taxonomy of this species. For this purpose, 10 microsatellite loci were genotyped for 156 individuals of P. jauruensis. To provide a proxy for the expected interspecific differentiation level within this allopatric system, two populations (49 individuals) of P. vilaboensis (a species closely related to P. jauruensis) were also included. Additionally, two cpDNA markers (trnSGCU-trnGUCC and trnT-trnL) for a subsample of 44 individuals of both species were sequenced. The results obtained showed that even though P. jauruensis populations are relatively small and isolated, they still maintain a high level of genetic diversity (e.g., H_E = 0.557 to 0.725; H_O = 0.253 to 0.409). The study suggests the existence of two distinct taxa/evolutionary lineages through their entire distribution. Two populations found in the same geographic region of the now synonymized P. densivillosus showed significant genetic divergence when compared with other populations of P. jauruensis. In contrast, our results did not support an evolutionary independence hypothesis for populations that occur in the same geographic region of the synonymous P. saudadensis.     

Seed storage of Brazilian cacti species in different threat categories

Cactaceae is considered the fifth most endangered taxonomic group. In light of this, the aim of this study was to evaluate the efficiency of different low‐temperature storage techniques in maintaining the viability of seeds of cacti in different threat categories. Seeds of six cacti taxa were stored in a cold chamber (8°C), a freezer (?5°C), in liquid nitrogen (?196°C) and at room temperature (25–27°C) for a period of 0, 1, 3, 6, 9 and 13 months. At each evaluation interval we removed a seed sample for each taxon studied, which was distributed into four repetitions of 25 seeds maintained at room temperature under 12‐h light/dark photoperiods. We evaluated the germinability, mean germination time and synchronization index. Most of the studied taxa presented germinability of above 50%, which was influenced by time and by storage temperatures. Also, most taxa stored at room temperature presented a significant reduction in germinability, whereas almost all taxa showed maintenance of the seed viability when stored in a cold chamber, a freezer or liquid nitrogen. This response can be justified by the reduction of the seed metabolism and the degradation of the reserve compounds of the seeds while at lower temperatures. Our results indicate that storage at low temperatures is an effective method for the conservation of cacti seeds and can be used for the formation of artificial seed banks of threatened cacti species.     

Johansson revisited: the spatial structure of epiphyte assemblages

Question: Vertical zonation schemes are widely used in biodiversity studies with vascular epiphytes as a tool to capture spatial distribution patterns, the one most commonly used was proposed by Johansson more than 30 years ago. Does a survey of the epiphytes found on larger trees really yield a representative sample of the local community? Location: Lowland rainforest of the San Lorenzo Crane Plot, Republic of Panama. Methods: A complete census of the vascular epiphytes on all trees > 1 cm DBH in 0.4 ha of undisturbed lowland forest was analysed with both cluster and discriminant analysis to detect groupings of epiphyte species. Results: Six different groups of species were detected, five of them preferring different substrates on larger trees (as defined by (1) the height above ground at the attachment site, (2) the diameter of the substrate and (3) the occurrence on stem vs branches/twigs) and resembling to some extent the original Johansson zones. A sixth group of epiphytes, comprising ca. 10% of all taxa, was almost always found on small diameter stems and branches of trees with small DBH at lower and intermediate heights within the forest. Conclusions: Applying pre‐established zonation schemes may lead to misleading results in biodiversity studies with epiphytes. Important aspects of spatial distribution patterns may be missed, and the determination of relative species abundances may carry a strong quantitative and qualitative bias when analyses rely completely on epiphytic plants found on larger trees.     

How and why does the areole meristem move in Echinocereus (Cactaceae)?

Background and Aims In Cactaceae, the areole is the organ that forms the leaves, spines and buds. Apparently, the genus Echinocereus develops enclosed buds that break through the epidermis of the stem adjacent to the areole; this trait most likely represents a synapomorphy of Echinocereus. The development of the areole is investigated here in order to understand the anatomical modifications that lead to internal bud development and to supplement anatomical knowledge of plants that do not behave according to classical shoot theory.Methods The external morphology of the areole was documented and the anatomy was studied using tissue clearing, scanning electron microscopy and light microscopy for 50 species that represent the recognized clades and sections of the traditional classification of the genus, including Morangaya pensilis (Echinocereus pensilis).Key Results In Echinocereus, the areole is sealed by the periderm, and the areole meristem is moved and enclosed by the differential growth of the epidermis and surrounding cortex. The enclosed areole meristem is differentiated in a vegetative or floral bud, which develops internally and breaks through the epidermis of the stem. In Morangaya pensilis, the areole is not sealed by the periderm and the areole meristem is not enclosed.Conclusions The enclosed areole meristem and internal bud development are understood to be an adaptation to protect the meristem and the bud from low temperatures. The anatomical evidence supports the hypothesis that the enclosed bud represents one synapomorphy for Echinocereus and also supports the exclusion of Morangaya from Echinocereus.     

Abscisic acid signal transduction in epidermal cells of Pisum sativum L. Argenteum: both dehydrin mRNA accumulation and stomatal responses require protein phosphorylation and dephosphorylation

The determinate growth of the primary root, its organization and relationship with lateral-root development, and the possible ecological significance of this growth pattern were analyzed in three sympatric species of Cactaceae from the Sonoran Desert, Stenocereus gummosus (Engelm.) Gibson & Horak, S. thurberi (Engelm.) Buxbaum and Ferocactus peninsulae (F.A.C. Weber) Britton & Rose, var. townsendianus (Britton & Rose) N.P. Taylor, stat. nov., Engelm. After seed germination, primary roots of these species commonly grew only for 2–3 d after the start of radicle protrusion (ASRP). This pattern of growth was observed on seedlings growing on filter paper, in vitro under sterile conditions, or in soil. The root-hair zone approached the very tip of the root and meristem exhaustion appeared to be typical in all seedlings of a population in all species. On average, 23 meristematic cells in the epidermal cell file in F. peninsulae were counted during the short steady-state period of growth (12–24 h ASRP). In S. gummosus, the size of the meristem was smaller with the number of epidermal cells in the meristem during the short steady-state growth period (12–36 h ASRP) averaging 13. The dynamics of meristem exhaustion obeyed Ivanov's model of the life span of cells in the meristem that states: if cell division is suppressed, half of the cells present in the meristem at a given time leave the meristem and start elongation during the period equal to the duration of the cell division cycle. It was deduced, on average, three to five cell division cycles in the meristem preceded its exhaustion. The lost meristem integrity can be related to only a few initial cells being found in the radicle. The cessation of meristematic activity in the primary-root apical meristem was directly related to the induction of lateral-root formation. Determinate primary-root growth can be thus viewed as a physiological root-tip decapitation that stops production of a signal inhibiting lateral-root primordia initiation. The time of lateral-root formation in S. gummosus and F. peninsulae was equal to or shorter than in agronomic mezophyte plants. Lateral roots also had determinate growth. The rapidity of root-system development and the ability to stop and to continue growth at any time under unfavorable and favorable conditions suggests the important role of determinate growth in seedling establishment of these Sonoran Desert species. Received: 13 December 1996 / Accepted: 6 January 1997     

Flower flavonoids of Opuntia subgenus Cylindropuntia

Flavonoids were identified by PC and HPLC from the flowers of three cholla species and their known diploid and triploid hybrids. All the individuals examined produce quercetin 3-glucoside, quercetin 3-rutinoside and kaempferol 3-glucoside, which vary quantitatively among taxa.