Limited effects of xylem anatomy on embolism resistance in cycad leaves.

Drought-induced xylem embolism is a primary cause of plant mortality. Although c. 70% of cycads are threatened by extinction and extant cycads diversified during a period of increasing aridification, the vulnerability of cycads to embolism spread has been overlooked. We quantified the vulnerability to drought-induced embolism, pressure-volume curves, in situ water potentials, and a suite of xylem anatomical traits of leaf pinnae and rachises for 20 cycad species. We tested whether anatomical traits were linked to hydraulic safety in cycads. Compared with other major vascular plant clades, cycads exhibited similar embolism resistance to angiosperms and pteridophytes but were more vulnerable to embolism than noncycad gymnosperms. All 20 cycads had both tracheids and vessels, the proportions of which were unrelated to embolism resistance. Only vessel pit membrane fraction was positively correlated to embolism resistance, contrary to angiosperms. Water potential at turgor loss was significantly correlated to embolism resistance among cycads. Our results show that cycads exhibit low resistance to xylem embolism and that xylem anatomical traits - particularly vessels - may influence embolism resistance together with tracheids. This study highlights the importance of understanding the mechanisms of drought resistance in evolutionarily unique and threatened lineages like the cycads.

Population genomics highlights structural variations in local adaptation to saline coastal environments in woolly grape.

Structural variations (SVs) are a feature of plant genomes that has been largely unexplored despite their significant impact on plant phenotypic traits and local adaptation to abiotic and biotic stress. In this study, we employed woolly grape (Vitis retordii), a species native to the tropical and subtropical regions of East Asia with both coastal and inland habitats, as a valuable model for examining the impact of SVs on local adaptation. We assembled a haplotype-resolved chromosomal reference genome for woolly grape, and conducted population genetic analyses based on whole-genome sequencing (WGS) data from coastal and inland populations. The demographic analyses revealed recent bottlenecks in all populations and asymmetric gene flow from the inland to the coastal population. In total, 1,035 genes associated with plant adaptive regulation for salt stress, radiation, and environmental adaptation were detected underlying local selection by SVs and SNPs in the coastal population, of which 37.29% and 65.26% were detected by SVs and SNPs, respectively. Candidate genes such as FSD2, RGA1, and AAP8 associated with salt tolerance were found to be highly differentiated and selected during the process of local adaptation to coastal habitats in SV regions. Our study highlights the importance of SVs in local adaptation; candidate genes related to salt stress and climatic adaptation to tropical and subtropical environments are important genomic resources for future breeding programs of grapevine and its rootstocks.

Diverse mangroves deviate from other angiosperms in their genome size, leaf cell size and cell packing density relationships.

BACKGROUND AND AIMS: While genome size limits the minimum sizes and maximum numbers of cells that can be packed into a given leaf volume, mature cell sizes can be substantially larger than their meristematic precursors and vary in response to abiotic conditions. Mangroves are iconic examples of how abiotic conditions can influence the evolution of plant phenotypes. METHODS: Here, we examined the coordination between genome size, leaf cell sizes, cell packing densities and leaf size in 13 mangrove species across four sites in China. Four of these species occurred at more than one site, allowing us to test the effect of climate on leaf anatomy. RESULTS: We found that genome sizes of mangroves were very small compared to other angiosperms, but, like other angiosperms, mangrove cells were always larger than the minimum size defined by genome size. Increasing mean annual temperature of a growth site led to higher packing densities of veins (Dv) and stomata (Ds) and smaller epidermal cells but had no effect on stomatal size. In contrast to other angiosperms, mangroves exhibited (1) a negative relationship between guard cell size and genome size; (2) epidermal cells that were smaller than stomata; and (3) coordination between Dv and Ds that was not mediated by epidermal cell size. Furthermore, mangrove epidermal cell sizes and packing densities covaried with leaf size. CONCLUSIONS: While mangroves exhibited coordination between veins and stomata and attained a maximum theoretical stomatal conductance similar to that of other angiosperms, the tissue-level tradeoffs underlying these similar relationships across species and environments were markedly different, perhaps indicative of the unique structural and physiological adaptations of mangroves to their stressful environments.

Coordination of intertracheid pit traits and climate effects among cycads.

Interconduit pit membranes, which are permeable regions in the primary cell wall that connect to adjacent conduits, play a crucial role in water relations and the movement of nutrients between xylem conduits. However, how pit membrane characteristics might influence water-carbon coupling remains poorly investigated in cycads. We examined pit characteristics, the anatomical and photosynthetic traits of 13 cycads from a common garden, to determine if pit traits and their coordination are related to water relations and carbon economy. We found that the pit traits of cycads were highly variable and that cycads exhibited a similar tradeoff between pit density and pit area as other plant lineages. Unlike other plant lineages (1) pit membranes, pit apertures, and pit shapes of cycads were not coordinated as in angiosperms; (2) cycads exhibited larger pit membrane areas but lower pit densities relative to ferns and angiosperms, but smaller and similar pit membrane densities to non-cycad gymnosperms; (3) cycad pit membrane areas and densities were partially coordinated with anatomical traits, with hydraulic supply of the rachis positively coordinated with photosynthesis, whereas pit aperture areas and fractions were negatively coordinated with photosynthetic traits; (4) cycad pit traits reflected adaptation to wetter habitats for Cycadaceae and drier habitats for Zamiaceae. The large variation in pit traits, the unique pit membrane size and density, and the partial coordination of pit traits with anatomical and physiological traits of the rachis and pinna among cycads may have facilitated their dominance in a variety of ecosystems from the Mesozoic to modern times.

Hydraulic traits are more diverse in flowers than in leaves.

Maintaining water balance has been a critical constraint shaping the evolution of leaf form and function. However, flowers, which are heterotrophic and relatively short-lived, may not be constrained by the same physiological and developmental factors. We measured physiological parameters derived from pressure-volume curves for leaves and flowers of 22 species to characterize the diversity of hydraulic traits in flowers and to determine whether flowers are governed by the same constraints as leaves. Compared with leaves, flowers had high saturated water content, which was a strong predictor of hydraulic capacitance in both leaves and flowers. Principal component analysis revealed that flowers occupied a different region of multivariate trait space than leaves and that hydraulic traits are more diverse in flowers than in leaves. Without needing to maintain high rates of transpiration, flowers rely on other hydraulic traits, such as high hydraulic capacitance, to maintain turgor pressure. As a result, instead of employing a metabolically expensive but durable carbon (C)-based skeleton, flowers may rely predominantly on a metabolically cheaper, hydrostatic skeleton to keep their structures on display for pollinators, which has important implications for both the costs of reproduction and the biomechanical performance of flowers, particularly during drought.

Asymmetric Synthesis of 1,1,1-Triarylethanes by Chiral Imidodiphosphoric Acid Catalyzed Nucleophilic Addition of Pyrrole and Indoles to 3-Vinylindoles.

Chiral imidodiphosphoric acids were employed as efficient catalysts in the enantioselective addition reaction of pyrrole and indoles to 3-vinylindoles. A series of optically active 1,1,1-triarylethmanes bearing quaternary stereocenters were synthesized in excellent yields (up to 99% yield) and enantioselectivities (up to 98% ee). Gram-scale reactions of 1i and 2a as well as 1o and 5a demonstrated the synthetic utility of this methodology. Control experiments showed that the formation of a double H-bond between the catalyst and substrates is necessary for an excellent outcome.

RpfC regulates the expression of the key regulator hrpX of the hrp/T3SS system in Xanthomonas campestris pv. campestris.

BACKGROUND: The Gram-negative phytopathogenic bacterium Xanthomonas campestris pv. campestris recruits the hrp/T3SS system to inject pathogenicity effector proteins into host cells and uses the rpf/DSF cell-cell signaling system to regulate the expression of virulence factors such as extracellular enzymes and polysaccharide. Whether these two systems have any connection is unknown. METHODS: Positive regulator candidates affecting hrpX expression were identified by sacB strategy. The transcriptional expression was determined by qRT-PCR and GUS activity analysis. Transcriptome analysis was performed by RNA deep-sequencing. The hypersensitive response (HR) was determined in the nonhost plant pepper ECW-10R and electrolyte leakage assay. RESULTS: Mutation of the gene encoding the sensor RpfC of the rpf/DSF system significantly reduced the expression of hrpX, the key regulator of the hrp/T3SS system, all of the genes in the hrp cluster and most reported type III effector genes. Mutation of rpfG did not affect the expression of hrpX. The rpfC mutant showed a delayed and weakened HR induction. CONCLUSIONS: RpfC positively regulates the expression of hrpX independent of RpfG, showing a complex regulatory network linking the rpf/DSF and hrp/T3SS systems.

Hydraulic differences between flowers and leaves are driven primarily by pressure-volume traits and water loss.

Flowers are critical for successful reproduction and have been a major axis of diversification among angiosperms. As the frequency and severity of droughts are increasing globally, maintaining water balance of flowers is crucial for food security and other ecosystem services that rely on flowering. Yet remarkably little is known about the hydraulic strategies of flowers. We characterized hydraulic strategies of leaves and flowers of ten species by combining anatomical observations using light and scanning electron microscopy with measurements of hydraulic physiology (minimum diffusive conductance (g min) and pressure-volume (PV) curves parameters). We predicted that flowers would exhibit higher g min and higher hydraulic capacitance than leaves, which would be associated with differences in intervessel pit traits because of their different hydraulic strategies. We found that, compared to leaves, flowers exhibited: 1) higher g min, which was associated with higher hydraulic capacitance (C T); 2) lower variation in intervessel pit traits and differences in pit membrane area and pit aperture shape; and 3) independent coordination between intervessel pit traits and other anatomical and physiological traits; 4) independent evolution of most traits in flowers and leaves, resulting in 5) large differences in the regions of multivariate trait space occupied by flowers and leaves. Furthermore, across organs intervessel pit trait variation was orthogonal to variation in other anatomical and physiological traits, suggesting that pit traits represent an independent axis of variation that have as yet been unquantified in flowers. These results suggest that flowers, employ a drought-avoidant strategy of maintaining high capacitance that compensates for their higher g min to prevent excessive declines in water potentials. This drought-avoidant strategy may have relaxed selection on intervessel pit traits and allowed them to vary independently from other anatomical and physiological traits. Furthermore, the independent evolution of floral and foliar anatomical and physiological traits highlights their modular development despite being borne from the same apical meristem.

Characterization of the complete chloroplast genome of mangrove Rhizophora apiculata Blume (Rhizophoraceae).

The chloroplast (cp) genome sequence of Rhizophora apiculata was characterized. The cp genome length was 164,343 bp in length, containing a typical structure of a large single copy (LSC) of 93,155 bp, a small single copy (SSC) of 19,376 bp, and two inverted repeats (IRs) of 25,906 bp, with a GC content of 34.9%. There were 131 genes were annotated in the cp genome, including 85 protein-coding genes, 38 tRNA genes, and 8 rRNA genes. A phylogenetic analysis using cp genomes of mangroves and ecologically associated species resolved R. apiculata in Rhizophora with R. stylosa and R. x lamarckii. This complete chloroplast sequence offers a promising tool for further species identification and evolutionary studies of Rhizophora, as well as for mangroves.

Characterization of the complete chloroplast genome of mangrove Bruguiera gymnorrhiza (L.) Lam. ex Savigny.

The chloroplast (cp) genome sequence of Bruguiera gymnorrhiza was characterized. The cp genome length was 163,795 bp in length, with a GC content of 35.3%, containing a large single copy (LSC) of 90,830 bp, a small single copy (SSC) of 20,207 bp, and a pair of inverted repeats (IRs) of 26,379 bp. The genome contained 121 genes, including 84 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. A phylogenetic analysis using cp genomes of mangroves and ecologically associated species resolved B. gymnorrhiza in Bruguiera with B. sexangula var. rhynchopetala. This complete chloroplast sequence offers a promising tool for further species identification and evolutionary studies of Bruguiera, as well as for mangroves.

The C-terminal domain of the type III secretion chaperone HpaB contributes to dissociation of chaperone-effector complex in Xanthomonas campestris pv. campestris.

Many animal and plant pathogenic bacteria employ a type three secretion system (T3SS) to deliver type three effector proteins (T3Es) into host cells. Efficient secretion of many T3Es in the plant pathogen Xanthomonas campestris pv. campestris (Xcc) relies on the global chaperone HpaB. However, how the domain of HpaB itself affects effector translocation/secretion is poorly understood. Here, we used genetic and biochemical approaches to identify a novel domain at the C-terminal end of HpaB (amino acid residues 137-160) that contributes to virulence and hypersensitive response (HR). Both in vitro secretion assay and in planta translocation assay showed that the secretion and translocation of T3E proteins depend on the C-terminal region of HpaB. Deletion of the C-terminal region of HpaB did not affect binding to T3Es, self-association or interaction with T3SS components. However, the deletion of C-terminal region sharply reduced the mounts of free T3Es liberated from the complex of HpaB with the T3Es, a reaction catalyzed in an ATP-dependent manner by the T3SS-associated ATPase HrcN. Our findings demonstrate the C-terminal domain of HpaB contributes to disassembly of chaperone-effector complex and reveal a potential molecular mechanism underpinning the involvement of HpaB in secretion of T3Es in Xcc.

[Effect of Huangqi decoction on delaying renal cell apoptosis induced by 12C6+ ion irradiation in rats and its mechanism].

Objective: To investigate the molecular protective mechanisms of Huangqi decoction inhibiting the apoptosis of renal cells in the 12C6+ radiation brain model rats. Methods: Fifty Wistar rats were randomly divided into five groups: normal control group, radiation alone model group, Huangqi decoction (high-dose, middle-dose and low-dose ) groups. The normal control group and the radiation alone group were treated with saline10 ml/(kg·d) by gavage, the Huangqi decoction treatment groups were treated with Huangqi decoction at the doses of 4.5, 9 and 18 g/(kg·d) by gavage respectively. After 7 d, except mice in normal control group, the brain of the rats in radiation alone model group, high-dose, middle-dose and low-dose Huangqi decoction group were radiated by 4 Gy 12C6+ ion once. The rats were killed by the femoral artery after irradiation 7 d. The pathomorphism changes of renal tissue were observed by HE, the IL-6 level in serum was detected by ELISA, the gene expressions of Bcl-2, Bax and caspase-3 in renal tissue were assessed by RT-PCR, and the protein expressions of Bcl-2, Bax, caspase-3 and NF-κB in renal tissue were analyzed by immunehistochemical staining. Results: Compared with normal control group, the body weight and kidney index were decreased significantly, the expression of Bcl-2 in renal tissue was decreased significantly, the serum content of IL-6 was increased obviously, and the expressions of Bax, caspase-3 and NF-κB in renal tissue were increased significantly in the radiation alone model group (P＜0.01). The mesangial cells proliferated obviously, interstitial vessels of renal tubules were dilated and congested obviously, the lumen of renal tubules was narrow and irregular in the radiation alone model group. As compared with the radiation alone model group, the body weight and the kidney index were increased obviously in high-dose Huangqi decoction group, the gene and protein expressions of Bcl-2 in renal tissue were increased significantly in Huangqi decoction intervention group(P＜0.05 or P＜0.01). whereas, the protein expressions of Bax and caspase-3 in renal tissue were decreased significantly in middle-dose and high-dose Huangqi decoction group, the serum content of IL-6 was decreased obviously, the gene expressions of Bax and caspase-3 in renal tissue were decreased significantly and the protein expression of NF-κB in renal tissue was decreased significantly in Huangqi decoction intervention group(P＜0.05 or P＜0.01). The proliferation of mesangial cells was improved and the contour of renal tubules was clear in high-dose huangqi decoction group. Conclusion: High-dose of huangqi decoction has protective effect on kidney in rats induced by 12C6+ radiation brain, the mechanism may be related to the regulation of Bcl-2/NF-κB signal pathway.

Identification of six type III effector genes with the PIP box in Xanthomonas campestris pv. campestris and five of them contribute individually to full pathogenicity.

Xanthomonas campestris pv. campestris is the pathogen of black rot of cruciferous plants. The pathogenicity of the pathogen depends on the type III secretion system (T3SS) that translocates directly effector proteins into plant cells, where they play important roles in the molecular interaction between the pathogen and its hosts. The T3SS of Xanthomonas spp. is encoded by a cluster of hypersensitive response and pathogenicity (hrp) genes. It has been demonstrated that the expression of hrp genes and some type III secreted (T3S)-effector genes is coactivated by the key hrp regulatory protein HrpX. The regulation by HrpX can be mediated by the binding of HrpX protein to a cis-regulatory element named the plant-inducible promoter (PIP) box present in the promoter region of HrpX-regulated genes. A genome screen revealed that X. campestris pv. campestris 8004 possesses 56 predicted genes with the PIP box. Nine of these genes have been shown to encode T3S effectors, Hrp, and Hrp-associated proteins. In this study, we employed an established T3S effector translocation assay with the hypersensitive-reaction-inducing domain of X. campestris pv. campestris AvrBs1 as a reporter to characterize the remaining 47 genes with the PIP box and showed that 6 of them, designated as XopXccE1, XopXccP, XopXccQ, XopXccR1, XopXccLR, and AvrXccB, harbor a functional translocation signal in their N-terminal regions, indicating that they are T3S effectors of X. campestris pv. campestris. We provided evidence to demonstrate that all these effectors are expressed in an HrpX-dependent manner and their translocation into plant cells relies on the translocon protein HrpF and the chaperone HpaB. Mutational analyses demonstrated that all these effectors, except AvrXccB, are individually required for full virulence and growth of X. campestris pv. campestris in the host plant Chinese radish.

The type III secretion effector XopXccN of Xanthomonas campestris pv. campestris is required for full virulence.

XopN was originally identified from Xanthomonas campestris pv. vesicatoria as an effector translocated into plant cells via the type III secretion system (T3SS), and is required for pathogenicity. We report here that the xopN homologue in the X. campestris pv. campestris genome, named xopXccN, also encodes a T3SS effector and is required for full virulence. We further demonstrate that expression of xopXccN is positively regulated by the key hrp (hypersensitive response and pathogenicity) regulators HrpG and HrpX.

Characterization of the complete chloroplast genome of endangered Cycads Zamia fischeri Miq. ex Lem.

The whole chloroplast (cp) genome sequence of Zamia fischeri has been characterized. The cp genome length was 164,767 bp in length, with a GC content of 39.7%, containing a large single copy (LSC) of 90,226 bp, a small single copy (SSC) of 23,223 bp, and a pair of inverted repeats (IRs) of 25,659 bp. The genome contained 127 genes, including 88 protein-coding genes, 31 tRNA genes, and 8 rRNA genes. A phylogenetic analysis based on complete chloroplast genomes in Cycads indicates that Z. fischeri clustered with another Zamia (Z. furfuracea). This complete chloroplast sequence offers a promising tool for further species identification, population genetic conservation, and evolutionary studies of Zamiaceae, as well as for Cycadales.

The complete mitochondrial genome of the Basidiomycete fungus Pleurotus cornucopiae (Paulet) Rolland.

Pleurotus cornucopiae is a commercial edible and medicinal fungus. Herein, we determined and analyzed its complete mitochondrial genome. The mitogenome length was 72,134 bp with a GC content of 26.7%, contained 14 conserved protein coding genes, two rRNA genes (rnl and rns), ribosomal protein gene rps3 and 24 tRNA genes. Pleurotus cornucopiae has a similar gene content and gene order of the mitogenome as P. ostreatus and P. eryngii. A phylogenetic analysis based on complete mitogenome in related fungi showed that P. cornucopiae is a member of the order Agaricales, forming a clade with P. ostreatus and P. eryngii, with P. ostreatus as a sister taxa. The mitochondrial genome sequence of P. cornucopiae appeared a promising tool for further studies of the taxonomy and evolution of Pleurotaceae and Agaricales.

Leaf turgor loss point is correlated with drought tolerance and leaf carbon economics traits.

Leaf turgor loss point (πtlp) indicates the capacity of a plant to maintain cell turgor pressure during dehydration, which has been proven to be strongly predictive of the plant response to drought. In this study, we compiled a data set of πtlp for 1752 woody plant individuals belonging to 389 species from nine major woody biomes in China, along with reduced sample size of hydraulic and leaf carbon economics data. We aimed to investigate the variation of πtlp across biomes varying in water availability. We also tested two hypotheses: (i) πtlp predicts leaf hydraulic safety margins and (ii) it is correlated with leaf carbon economics traits. Our results showed that there was a positive relationship between πtlp and aridity index: biomes from humid regions had less negative values than those from arid regions. This supports the idea that πtlp may reflect drought tolerance at the scale of woody biomes. As expected, πtlp was significantly positively correlated with leaf hydraulic safety margins that varied significantly across biomes, indicating that this trait may be useful in modelling changes of forest components in response to increasing drought. Moreover, πtlp was correlated with a suite of coordinated hydraulic and economics traits; therefore, it can be used to predict the position of a given species along the 'fast-slow' whole-plant economics spectrum. This study expands our understanding of the biological significance of πtlp not only in drought tolerance, but also in the plant economics spectrum.

The complete mitochondrial genome of the Agrocybe aegerita, an edible mushroom.

Agrocybe aegerita is a medicinally and nutritionally important edible basidiomycete. Despite previous phylogenetic studies, the taxonomy of A. aegerita complex remains unclear due to lacking of resolutive data. Herein, the complete mitochondrial genome of A. aegerita is reported and analyzed. The mitogenome length was 116,329 bp, with a GC content of 27.6%, include 17 typical protein-coding genes, two ribosomal protein genes (rps3), two ribosomal RNA genes and a set of 32 transfer RNA genes. A phylogenetic analyses using complete mitogenome in Agaricales showed that A. aegerita is closely related to the genus Pleurotus and represents a clade clearly independent from other Agaricales species.

Salt management strategy defines the stem and leaf hydraulic characteristics of six mangrove tree species.

Mangroves in hypersaline coastal habitats are under constant high xylem tension and face great risk of hydraulic dysfunction. To investigate the relationships between functional traits and salt management, we measured 20 hydraulic and photosynthetic traits in four salt-adapted (SA) and two non-SA (NSA) mangrove tree species in south China. The SA species included two salt secretors (SSs), Avicennia marina (Forsskål) Vierhapper and Aegiceras corniculatum (L.) Blanco and two salt excluders (SEs), Bruguiera gymnorrhiza (L.) Savigny and Kandelia obovata (L.) Sheue et al. The two NSA species were Hibiscus tiliaceus (L.) and Pongamia pinnata (L.) Merr. Extremely high xylem cavitation resistance, indicated by water potential at 50% loss of xylem conductivity (Ψ50; -7.85 MPa), was found in SEs. Lower cavitation resistance was observed in SSs, and may result from incomplete salt removal that reduces the magnitude of xylem tension required to maintain water uptake from the soil. Surprisingly, the NSA species, P. pinnata, had very low Ψ50 (-5.44 MPa). Compared with NSAs, SAs had lower photosynthesis, vessel density, hydraulic conductivity and vessel diameter, but higher sapwood density. Eight traits were strongly associated with species' salt management strategies, with predawn water potential (ΨPD) and mean vessel diameter accounting for 95% flow (D95) having the most significant association; D95 separated SAs from NSAs and SEs had the lowest ΨPD. There was significant coupling between hydraulic traits and carbon assimilation traits. Instead of hydraulic safety being compromised by xylem efficiency, mangrove species with higher safety had higher efficiency and greater sapwood density (ρSapwood), but there was no relationship between ρSapwood and efficiency. Principal component analysis differentiated the species of the three salt management strategies by loading D, D95 and vessel density on the first axis and loading ΨPD, Ψ50 and water potential at 12% loss of xylem conductivity (Ψ12), ρSapwood and quantum yield on the second axis. Our results provide the first comparative characterization of hydraulic and photosynthetic traits among mangroves with different salt management strategies.

Comparison of intraspecific, interspecific and intergeneric chloroplast diversity in Cycads.

Cycads are among the most threatened plant species. Increasing the availability of genomic information by adding whole chloroplast data is a fundamental step in supporting phylogenetic studies and conservation efforts. Here, we assemble a dataset encompassing three taxonomic levels in cycads, including ten genera, three species in the genus Cycas and two individuals of C. debaoensis. Repeated sequences, SSRs and variations of the chloroplast were analyzed at the intraspecific, interspecific and intergeneric scale, and using our sequence data, we reconstruct a phylogenomic tree for cycads. The chloroplast was 162,094 bp in length, with 133 genes annotated, including 87 protein-coding, 37 tRNA and 8 rRNA genes. We found 7 repeated sequences and 39 SSRs. Seven loci showed promising levels of variations for application in DNA-barcoding. The chloroplast phylogeny confirmed the division of Cycadales in two suborders, each of them being monophyletic, revealing a contradiction with the current family circumscription and its evolution. Finally, 10 intraspecific SNPs were found. Our results showed that despite the extremely restricted distribution range of C. debaoensis, using complete chloroplast data is useful not only in intraspecific studies, but also to improve our understanding of cycad evolution and in defining conservation strategies for this emblematic group.