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Land plant aerial organs are covered by a hydrophobic layer called the cuticle that serves as a waterproof barrier protecting plants against desiccation, ultraviolet radiation, and pathogens. Cuticle consists of a cutin matrix as well as cuticular waxes in which very-long-chain (VLC) alkanes are the major components, representing up to 70% of the total wax content in Arabidopsis (Arabidopsis thaliana) leaves. However, despite its major involvement in cuticle formation, the alkane-forming pathway is still largely unknown. To address this deficiency, we report here the characterization of the Arabidopsis ECERIFERUM1 (CER1) gene predicted to encode an enzyme involved in alkane biosynthesis. Analysis of CER1 expression showed that CER1 is specifically expressed in the epidermis of aerial organs and coexpressed with other genes of the alkane-forming pathway. Modification of CER1 expression in transgenic plants specifically affects VLC alkane biosynthesis: waxes of TDNA insertional mutant alleles are devoid of VLC alkanes and derivatives, whereas CER1 overexpression dramatically increases the production of the odd-carbon-numbered alkanes together with a substantial accumulation of iso-branched alkanes. We also showed that CER1 expression is induced by osmotic stresses and regulated by abscisic acid. Furthermore, CER1-overexpressing plants showed reduced cuticle permeability together with reduced soil water deficit susceptibility. However, CER1 overexpression increased susceptibility to bacterial and fungal pathogens. Taken together, these results demonstrate that CER1 controls alkane biosynthesis and is highly linked to responses to biotic and abiotic stresses.

The helical coiling of plant tendrils has fascinated scientists for centuries, yet the underlying mechanism remains elusive. Moreover, despite Darwin's widely accepted interpretation of coiled tendrils as soft springs, their mechanical behavior remains unknown. Our experiments on cucumber tendrils demonstrate that tendril coiling occurs via asymmetric contraction of an internal fiber ribbon of specialized cells. Under tension, both extracted fiber ribbons and old tendrils exhibit twistless overwinding rather than unwinding, with an initially soft response followed by strong strain-stiffening at large extensions. We explain this behavior using physical models of prestrained rubber strips, geometric arguments, and mathematical models of elastic filaments. Collectively, our study illuminates the origin of tendril coiling, quantifies Darwin's original proposal, and suggests designs for biomimetic twistless springs with tunable mechanical responses.

A CBL-interacting protein kinase (CIPK) gene, BnCIPK6, was isolated in Brassica napus. Through yeast two-hybrid screening, 27 interaction partners (including BnCBL1) of BnCIPK6 were identified in Brassica napus. Interaction of BnCIPK6 and BnCBL1 was further confirmed by BiFC (bimolecular fluorescence complementation) in plant cells. Expressions of BnCIPK6 and BnCBL1 were significantly up-regulated by salt and osmotic stresses, phosphorous starvation, and abscisic acid (ABA). Furthermore, BnCIPK6 promoter activity was intensively induced in cotyledons and roots under NaCl, mannitol, and ABA treatments. Transgenic Arabidopsis plants with over-expressing BnCIPK6, its activated form BnCIPK6M, and BnCBL1 enhanced high salinity and low phosphate tolerance, suggesting that the functional interaction of BnCBL1 and BnCIPK6 may be important for the high salinity and phosphorous deficiency signalling pathways. In addition, activation of BnCIPK6 confers Arabidopsis plants hypersensitive to ABA. On the other hand, over-expression of BnCIPK6 in Arabidopsis cipk6 mutant completely rescued the low-phosphate-sensitive and ABA-insensitive phenotypes of this mutant, further suggesting that BnCIPK6 is involved in the plant response to high-salinity, phosphorous deficiency, and ABA signalling.

The ARP2/3 complex, a highly conserved nucleator of F-actin, and its activator, the SCAR complex, are essential for growth in plants and animals. In this article, we present a pathway through which roots of Arabidopsis thaliana directly perceive light to promote their elongation. The ARP2/3-SCAR complex and the maintenance of longitudinally aligned F-actin arrays are crucial components of this pathway. The involvement of the ARP2/3-SCAR complex in light-regulated root growth is supported by our finding that mutants of the SCAR complex subunit BRK1/HSPC300, or other individual subunits of the ARP2/3-SCAR complex, showed a dramatic inhibition of root elongation in the light, which mirrored reduced growth of wildtype roots in the dark. SCAR1 degradation in dark-grown wild-type roots by constitutive photomorphogenic 1 (COP1) E3 ligase and 26S proteasome accompanied the loss of longitudinal F-actin and reduced root growth. Light perceived by the root photoreceptors, cryptochrome and phytochrome, suppressed COP1-mediated SCAR1 degradation. Taken together, our data provide a biochemical explanation for light-induced promotion of root elongation by the ARP2/3-SCAR complex.

The ability of plants to form mutualistic relationships with animal defenders has long been suspected to influence their evolutionary success, both by decreasing extinction risk and by increasing opportunity for speciation through an expanded realized niche. Nonetheless, the hypothesis that defense mutualisms consistently enhance plant diversification across lineages has not been well tested due to a lack of phenotypic and phylogenetic information. Using a global analysis, we show that the >100 vascular plant families in which species have evolved extrafloral nectaries (EFNs), sugar-secreting organs that recruit arthropod mutualists, have twofold higher diversification rates than families that lack species with EFNs. Zooming in on six distantly related plant clades, trait-dependent diversification models confirmed the tendency for lineages with EFNs to display increased rates of diversification. These results were consistent across methodological approaches. Inference using reversible-jump Markov chain Monte Carlo (MCMC) to model the placement and number of rate shifts revealed that high net diversification rates in EFN clades were driven by an increased number of positive rate shifts following EFN evolution compared with sister clades, suggesting that EFNs may be indirect facilitators of diversification. Our replicated analysis indicates that defense mutualisms put lineages on a path toward increased diversification rates within and between clades, and is concordant with the hypothesis that mutualistic interactions with animals can have an impact on deep macroevolutionary patterns and enhance plant diversity. Significance Plants that provide food and housing to animals in return for defense against enemies are classic examples of mutualistic partnerships in nature. Here, we show that the evolution of such plant–animal mutualisms also can lead to a trajectory of accelerated accumulation of plant species in the lineages that participate in these cooperative interactions. We found that the evolution of plant organs (extrafloral nectaries) that facilitate mutualisms with animal defenders was repeatedly followed by increased rates of diversification across distantly related plant lineages. These results suggest that by enabling ecological interactions with animals, the convergent evolution of relatively simple glands changed the course of plant evolution toward greater protection from pests and accelerated the generation of biodiversity.

Rapid detection of illicit opium poppy plants using UAV (unmanned aerial vehicle) imagery has become an important means to prevent and combat crimes related to drug cultivation. However, current methods rely on time-consuming visual image interpretation. Here, the You Only Look Once version 3 (YOLOv3) network structure was used to assess the influence that different backbone networks have on the average precision and detection speed of an UAV-derived dataset of poppy imagery, with MobileNetv2 (MN) selected as the most suitable backbone network. A Spatial Pyramid Pooling (SPP) unit was introduced and Generalized Intersection over Union (GIoU) was used to calculate the coordinate loss. The resulting SPP-GIoU-YOLOv3-MN model improved the average precision by 1.62% (from 94.75% to 96.37%) without decreasing speed and achieved an average precision of 96.37%, with a detection speed of 29 FPS using an RTX 2080Ti platform. The sliding window method was used for detection in complete UAV images, which took approximately 2.2 sec/image, approximately 10× faster than visual interpretation. The proposed technique significantly improved the efficiency of poppy detection in UAV images while also maintaining a high detection accuracy. The proposed method is thus suitable for the rapid detection of illicit opium poppy cultivation in residential areas and farmland where UAVs with ordinary visible light cameras can be operated at low altitudes (relative height < 200 m).

The allocation of the net primary productivity (NPP) of an ecosystem between canopy, woody tissue and fine roots is an important descriptor of the functioning of that ecosystem, and an important feature to correctly represent in terrestrial ecosystem models. Here, we collate and analyse a global dataset of NPP allocation in tropical forests, and compare this with the representation of NPP allocation in 13 terrestrial ecosystem models. On average, the data suggest an equal partitioning of allocation between all three main components (mean 34 ± 6% canopy, 39 ± 10% wood, 27 ± 11% fine roots), but there is substantial site-to-site variation in allocation to woody tissue versus allocation to fine roots. Allocation to canopy (leaves, flowers and fruit) shows much less variance. The mean allocation of the ecosystem models is close to the mean of the data, but the spread is much greater, with several models reporting allocation partitioning outside of the spread of the data. Where all main components of NPP cannot be measured, litterfall is a good predictor of overall NPP (r 2 = 0.83 for linear fit forced through origin), stem growth is a moderate predictor and fine root production a poor predictor. Across sites the major component of variation of allocation is a shifting allocation between wood and fine roots, with allocation to the canopy being a relatively invariant component of total NPP. This suggests the dominant allocation trade-off is a 'fine root versus wood' trade-off, as opposed to the expected 'root—shoot' trade-off; such a trade-off has recently been posited on theoretical grounds for old-growth forest stands. We conclude by discussing the systematic biases in estimates of allocation introduced by missing NPP components, including herbivory, large leaf litter and root exudates production. These biases have a moderate effect on overall carbon allocation estimates, but are smaller than the observed range in allocation values across sites.

Grasses possess basal and aerial axillary buds. Previous studies have largely focused on basal bud (tiller) formation but scarcely touched on aerial buds, which may lead to aerial branch development. Genotypes with and without aerial buds were identified in switchgrass (Panicum virgatum), a dedicated bioenergy crop. Bud development was characterized using scanning electron microscopy. Microarray, RNA-seq and quantitative reverse transcription polymerase chain reaction (RT-qPCR) were used to identify regulators of bud formation. Gene function was characterized by down-regulation and overexpression. Overexpression of miR156 induced aerial bud formation in switchgrass. Various analyses revealed that SQUAMOSA PROMOTER BINDING PROTEIN LIKE4 (SPL4), one of the miR156 targets, directly regulated aerial axillary bud initiation. Down-regulation of SPL4 promoted aerial bud formation and increased basal buds, while overexpression of SPL4 seriously suppressed bud formation and tillering. RNA-seq and RT-qPCR identified potential downstream genes of SPL4. Unlike all previously reported genes acting as activators of basal bud initiation, SPL4 acts as a suppressor for the formation of both aerial and basal buds. The miR156-SPL4 module predominantly regulates aerial bud initiation and partially controls basal bud formation. Genetic manipulation of SPL4 led to altered plant architecture with increased branching, enhanced regrowth after cutting and improved biomass yield.

Phenylalanine ammonia-lyase (PAL) is the first entry enzyme of the phenylpropanoid pathway, and therefore plays a key role in both plant development and stress defense. In many plants, PAL is encoded by a multi-gene family, and each member is differentially regulated in response to environmental stimuli. In the present study, we report that PAL in cucumber (Cucumis sativus L.) is encoded for by a family of seven genes (designated as CsPAL1-7). All seven CsPALs are arranged in tandem in two duplication blocks, which are located on chromosomes 4 and 6, respectively. The cDNA and protein sequences of the CsPALs share an overall high identity to each other. Homology modeling reveals similarities in their protein structures, besides several slight differences, implying the different activities in conversion of phenylalanine. Phylogenic analysis places CsPAL1-7 in a separate cluster rather than clustering with other plant PALs. Analyses of expression profiles in different cucumber tissues or in response to various stress or plant hormone treatments indicate that CsPAL1-7 play redundant, but divergent roles in cucumber development and stress response. This is consistent with our finding that CsPALs possess overlapping but different cis-elements in their promoter regions. Finally, several duplication events are discussed to explain the evolution of the cucumber PAL genes.

BACKGROUND: Carnivorous pitcher plants (CPPs) use cone-shaped leaves to trap animals for nutrient supply but are not able to kill all intruders of their traps. Numerous species, ranging from bacteria to vertrebrates, survive and propagate in the otherwise deadly traps. This paper reviews the literature on phytotelmata of CPPs. PITCHER FLUID AS A HABITAT: The volumes of pitchers range from 0·2 mL to 1·5 L. In Nepenthes and Cephalotus, the fluid is secreted by the trap; the other genera collect rain water. The fluid is usually acidic, rich in O₂ and contains digestive enzymes. In some taxa, toxins or detergents are found, or the fluid is extremely viscous. In Heliamphora or Sarracenia, the fluid differs little from pure water. INQUILINE DIVERSITY: Pitcher inquilines comprise bacteria, protozoa, algae, fungi, rotifers, crustaceans, arachnids, insects and amphibia. The dominant groups are protists and Dipteran larvae. The various species of CPPs host different sets of inquilines. Sarracenia purpurea hosts up to 165 species of inquilines, followed by Nepenthes ampullaria with 59 species, compared with only three species from Brocchinia reducta. Reasons for these differences include size, the life span of the pitcher as well as its fluid. MUTUALISTIC ACTIVITIES: Inquilines closely interact with their host. Some live as parasites, but the vast majority are mutualists. Beneficial activities include secretion of enzymes, feeding on the plant's prey and successive excretion of inorganic nutrients, mechanical break up of the prey, removal of excessive prey and assimilation of atmospheric N₂. CONCLUSIONS: There is strong evidence that CPPs influence their phytotelm. Two strategies can be distinguished: (1) Nepenthes and Cephalotus produce acidic, toxic or digestive fluids and host a limited diversity of inquilines. (2) Genera without efficient enzymes such as Sarracenia or Heliamphora host diverse organisms and depend to a large extent on their symbionts for prey utilization.