Flowering Plant Arabidopsis Thaliana Research Articles

Quantitative imaging reveals the role of MpARF proteasomal degradation during gemma germination

The auxin signaling molecule controls a variety of growth and developmental processes in land plants. Auxin regulates gene expression through a nuclear auxin signaling pathway (NAP) consisting of a ubiquitin ligase auxin receptor TIR1/AFB, its Aux/IAA degradation substrate, and DNA-binding ARF transcription factors. While extensive qualitative understanding of the pathway and its interactions has been obtained, mostly by studying the flowering plant Arabidopsis thaliana, it is so far unknown how these translate to quantitative system behaviour in vivo, a problem that is confounded by large NAP gene families in most species. Here we used the minimal NAP of the liverwort Marchantia polymorpha to quantitatively map NAP protein accumulation and dynamics in vivo through the use of knock-in fluorescent fusion proteins. Beyond revealing the dynamic native accumulation profile of the entire NAP protein network, we discovered that the two central ARFs, MpARF1 and MpARF2, are proteasomally degraded. This auxin-independent degradation tunes ARF protein stoichiometry to favor gene activation, thereby reprogramming auxin response during developmental progression. Thus, quantitative analysis of the entire NAP allowed us to identify ARF degradation and stoichiometries of activator and repressor ARFs as a potential mechanism for controlling gemma germination.

Control of stem cell behavior by CLE-JINGASA signaling in the shoot apical meristem in Marchantia polymorpha

Land plants undergo indeterminate growth by the activity of meristems in both gametophyte (haploid) and sporophyte (diploid) generations. In the sporophyte of the flowering plant Arabidopsis thaliana, the apical meristems are located at the shoot and root tips in which a number of regulatory gene homologs are shared for their development, implying deep evolutionary origins. However, little is known about their functional conservation with gametophytic meristems in distantly related land plants such as bryophytes, even thoughgenomic studies have revealed that the subfamily-level diversity of regulatory genes is mostly conserved throughout land plants. Here, we show that a NAM/ATAF/CUC (NAC) domain transcription factor, JINGASA (MpJIN), acts downstream of CLAVATA3 (CLV3)/ESR-related (CLE) peptide signaling and controls stem cell behavior in the gametophytic shoot apical meristem of the liverwort Marchantia polymorpha. In the meristem, strong MpJIN expression was associated with the periclinal cell division at the periphery of the stem cell zone (SCZ), whereas faint MpJIN expression was found at the center of the SCZ. Time course observation indicates that the MpJIN-negative cells are lost from the SCZ and respecified de novo at two separate positions during the dichotomous branching event. Consistently, the induction of MpJIN results in ectopic periclinal cell division in the SCZ and meristem termination. Based on the comparative expression data, we speculate that the function of JIN/FEZ subfamily genes was shared among the shoot apical meristems in the gametophyte and sporophyte generations in early land plants but was lost in certain lineages, including the flowering plant A.thaliana.

Divergence of trafficking and polarization mechanisms for PIN auxin transporters during land plant evolution

The phytohormone auxin, and its directional transport through tissues, plays a fundamental role in the development of higher plants. This polar auxin transport predominantly relies on PIN-FORMED (PIN) auxin exporters. Hence, PIN polarization is crucial for development, but its evolution during the rise of morphological complexity in land plants remains unclear. Here, we performed a cross-species investigation by observing the trafficking and localization of endogenous and exogenous PINs in two bryophytes, Physcomitrium patens and Marchantia polymorpha, and in the flowering plant Arabidopsis thaliana. We confirmed that the GFP fusion did not compromise the auxin export function of all examined PINs by using a radioactive auxin export assay and by observing the phenotypic changes in transgenic bryophytes. Endogenous PINs polarize to filamentous apices, while exogenous Arabidopsis PINs distribute symmetrically on the membrane in both bryophytes. In the Arabidopsis root epidermis, bryophytic PINs have no defined polarity. Pharmacological interference revealed a strong cytoskeletal dependence of bryophytic but not Arabidopsis PIN polarization. The divergence of PIN polarization and trafficking is also observed within the bryophyte clade and between tissues of individual species. These results collectively reveal the divergence of PIN trafficking and polarity mechanisms throughout land plant evolution and the co-evolution of PIN sequence-based and cell-based polarity mechanisms.

The plant response to high CO2 levels is heritable and orchestrated by DNA methylation.

Plant responses to abiotic environmental challenges are known to have lasting effects on the plant beyond the initial stress exposure. Some of these lasting effects are trans-generational, affecting the next generation. The plant response to elevated carbon dioxide (CO2 ) levels has been well studied. However, these investigations are typically limited to plants grown for a single generation in a high CO2 environment while trans-generational studies are rare. We aimed to determine trans-generational growth responses in plants after exposure to high CO2 by investigating the direct progeny when returned to baseline CO2 levels. We found that both the flowering plant Arabidopsis thaliana and seedless non-vascular plant Physcomitrium patens continue to display accelerated growth rates in the progeny of plants exposed to high CO2 . We used the model species Arabidopsis to dissect the molecular mechanism and found that DNA methylation pathways are necessary for heritability of this growth response. More specifically, the pathway of RNA-directed DNA methylation is required to initiate methylation and the proteins CMT2 and CMT3 are needed for the trans-generational propagation of this DNA methylation to the progeny plants. Together, these two DNA methylation pathways establish then maintain a cellular memory to high CO2 exposure.

Parallel evolution of two AIM24 protein subfamilies and their conserved functions in ER stress tolerance in land plants

Despite decades of efforts in genome sequencing and functional characterization, some important protein families remain poorly understood. In this study, we report the classification, evolution, and functions of the largely uncharacterized AIM24 protein family in plants, including the identification of a novel subfamily. We show that two AIM24 subfamilies (AIM24-A and AIM24-B) are commonly distributed in major plant groups. These two subfamilies not only have modest sequence similarities and different gene structures but also are of independent bacterial ancestry. We performed comparative functional investigations on the two AIM24 subfamilies using three model plants: the moss Physcomitrium patens, the liverwort Marchantia polymorpha, and the flowering plant Arabidopsis thaliana. Intriguingly, despite their significant differences in sequence and gene structure, both AIM24 subfamilies are involved in ER stress tolerance and the unfolded protein response (UPR). In addition, transformation of the AIM24-A gene from P. patens into the AIM24-B null mutant of A. thaliana could at least partially rescue ER stress tolerance and the UPR. We also discuss the role of AIM24 genes in plant development and other cellular activities. This study provides a unique example of parallel evolution in molecular functions and can serve as a foundation for further investigation of the AIM24 family in plants.

The single Marchantia polymorpha FERONIA homolog reveals an ancestral role in regulating cellular expansion and integrity.

Plant cells are surrounded by a cell wall, a rigid structure that is not only important for cell and organ shape, but is also crucial for intercellular communication and interactions with the environment. In the flowering plant Arabidopsis thaliana, the 17 members of the Catharanthus roseus RLK1-like (CrRLK1L) receptor kinase family are involved in a multitude of physiological and developmental processes, making it difficult to assess their primary or ancestral function. To reduce genetic complexity, we characterized the single CrRLK1L gene of Marchantia polymorpha, MpFERONIA (MpFER). Plants with reduced MpFER levels show defects in vegetative development, i.e. rhizoid formation and cell expansion, and have reduced male fertility. In contrast, cell integrity and morphogenesis of the gametophyte are severely affected in Mpfer null mutants and MpFER overexpression lines. Thus, we conclude that the CrRLK1L gene family originated from a single gene with an ancestral function in cell expansion and the maintenance of cellular integrity. During land plant evolution, this ancestral gene diversified to fulfill a multitude of specialized physiological and developmental roles in the formation of both gametophytic and sporophytic structures essential to the life cycle of flowering plants.

Modulation of receptor-like transmembrane kinase 1 nuclear localization by DA1 peptidases in Arabidopsis

The cleavage of intracellular domains of receptor-like kinases (RLKs) has an important functional role in the transduction of signals from the cell surface to the nucleus in many organisms. However, the peptidases that catalyze protein cleavage during signal transduction remain poorly understood despite their crucial roles in diverse signaling processes. Here, we report in the flowering plant Arabidopsis thaliana that members of the DA1 family of ubiquitin-regulated Zn metallopeptidases cleave the cytoplasmic kinase domain of transmembrane kinase 1 (TMK1), releasing it for nuclear localization where it represses auxin-responsive cell growth during apical hook formation by phosphorylation and stabilization of the transcriptional repressors IAA32 and IAA34. Mutations in DA1 family members exhibited reduced apical hook formation, and DA1 family-mediated cleavage of TMK1 was promoted by auxin treatment. Expression of the DA1 family-generated intracellular kinase domain of TMK1 by an auxin-responsive promoter fully restored apical hook formation in a tmk1 mutant, establishing the function of DA1 family peptidase activities in TMK1-mediated differential cell growth and apical hook formation. DA1 family peptidase activity therefore modulates TMK1 kinase activity between a membrane location where it stimulates acid cell growth and initiates an auxin-dependent kinase cascade controlling cell proliferation in lateral roots and a nuclear localization where it represses auxin-mediated gene expression and growth.

PROTECTION OF TELOMERES 1b Modulates Cellular ROS and Chromatin Structure in Arabidopsis thaliana

Reactive oxygen species (ROS) are natural by‐products of cellular respiration, essential for cell signaling. They are also a major threat to telomere stability and can trigger senescence. Emerging studies reveal a broad role for telomere‐associated factors in modulating the response to oxidative stress. PROTECTION OF TELOMERES 1 (POT1) is one of the most conserved telomeric proteins, critical for both chromosome‐end protection and replication. POT1 is a single‐copy gene in most species. However, the flowering plant Arabidopsis thaliana encodes two highly divergent POT1 paralogs, AtPOT1a and AtPOT1b. AtPOT1a is an essential telomerase‐associated processivity factor. In contrast, AtPOT1b is not required for telomere replication or end protection, and its overexpression cannot complement the loss of AtPOT1a. Here we explore the natural separation‐of‐function within Arabidopsis POT1 paralogs and uncover a novel role for AtPOT1b in redox homeostasis. AtPOT1b expression is highly regulated, and restricted to seeds, root tips, and gametophytes, organs whose development is controlled by endogenous ROS. Strikingly, ectopic over‐expression of AtPOT1b decreases natural ROS levels throughout the plant, while a null mutation results in high levels of cellular and genomic oxidation, telomere length changes under multiple environmental insults, decreased chromatin compaction, decreased DNA methylation and increased expression of stress‐response genes. Consequently, atpot1b mutants have reduced fitness and are hypersensitive to chemical and environmental stresses. Finally, in response to oxidative stress, AtPOT1b expression increases and the protein accumulates at telomeres, suggesting that AtPOT1b may play a direct role in mitigating telomere oxidation. We postulate that AtPOT1b functions in a molecular rheostat that both senses and regulates cellular oxidation, thereby promoting genome stability in tissues where higher ROS levels are required for development.

The mitochondrial copper chaperone COX11 has an additional role in cellular redox homeostasis.

Mitochondria are sites of cellular respiration, which is accompanied by the generation of dangerous reactive oxygen species (ROS). Cells have multiple mechanisms to mitigate the dangers of ROS. Here we investigate the involvement of the COX complex assembly chaperone COX11 (cytochrome c oxidase 11) in cellular redox homeostasis, using homologs from the flowering plant Arabidopsis thaliana (AtCOX11) and yeast Saccharomyces cerevisiae (ScCOX11). We found that AtCOX11 is upregulated in Arabidopsis seedlings in response to various oxidative stresses, suggesting a defensive role. In line with this, the overexpression of either AtCOX11 or ScCOX11 reduced ROS levels in yeast cells exposed to the oxidative stressor paraquat. Under normal growth conditions, both Arabidopsis and yeast COX11 overexpressing cells had the same ROS levels as the corresponding WT. In contrast, the COX11 knock-down and knock-out in Arabidopsis and yeast, respectively, significantly reduced ROS levels. In yeast cells, the ScCOX11 appears to be functionally redundant with superoxide dismutase 1 (ScSOD1), a superoxide detoxifying enzyme. The ΔSccox11ΔScsod1 mutants had dramatically reduced growth on paraquat, compared with the WT or single mutants. This growth retardation does not seem to be linked to the status of the COX complex and cellular respiration. Overexpression of putatively soluble COX11 variants substantially improved the resistance of yeast cells to the ROS inducer menadione. This shows that COX11 proteins can provide antioxidative protection likely independently from their COX assembly function. The conserved Cys219 (in AtCOX11) and Cys208 (in ScCOX11) are important for this function. Altogether, these results suggest that COX11 homologs, in addition to participating in COX complex assembly, have a distinct and evolutionary conserved role in protecting cells during heightened oxidative stress.

The Arabidopsis (ASHH2) CW domain binds monomethylated K4 of the histone H3 tail through conformational selection.

Chromatin post-translational modifications are thought to be important for epigenetic effects on gene expression. Methylation of histone N-terminal tail lysine residues constitutes one of many such modifications, executed by families of histone lysine methyltransferase (HKMTase). One such protein is ASHH2 from the flowering plant Arabidopsisthaliana, equipped with the interaction domain, CW, and the HKMTase domain, SET. The CW domain of ASHH2 is a selective binder of monomethylation at lysine 4 on histone H3 (H3K4me1) and likely helps the enzyme dock correctly onto chromatin sites. The study of CW and related interaction domains has so far been emphasizing lock-key models, missing important aspects of histone-tail CW interactions. We here present an analysis of the ASHH2 CW-H3K4me1 complex using NMR and molecular dynamics, as well as mutation and affinity studies of flexible coils. β-augmentation and rearrangement of coils coincide with changes in the flexibility of the complex, in particular the η1, η3 and C-terminal coils, but also in the β1 and β2 strands and the C-terminal part of the ligand. Furthermore, we show that mutating residues with outlier dynamic behaviour affect the complex binding affinity despite these not being in direct contact with the ligand. Overall, the binding process is consistent with conformational selection. We propose that this binding mechanism presents an advantage when searching for the correct post-translational modification state among the highly modified and flexible histone tails, and also that the binding shifts the catalytic SET domain towards the nucleosome. DATABASES: Structural data are available in the PDB database under the accession code 6QXZ. Resonance assignments for CW42 in its apo- and holo-forms are available in the BMRB database under the accession code 27251.

The Arabidopsis Hypoxia Inducible AtR8 Long Non-Coding RNA also Contributes to Plant Defense and Root Elongation Coordinating with WRKY Genes under Low Levels of Salicylic Acid.

AtR8 lncRNA was previously identified in the flowering plant Arabidopsis thaliana as an abundant Pol III-transcribed long non-coding RNA (lncRNA) of approximately 260 nt. AtR8 lncRNA accumulation is responsive to hypoxic stress and salicylic acid (SA) treatment in roots, but its function has not yet been identified. In this study, microarray analysis of an atr8 mutant and wild-type Arabidopsis indicated a strong association of AtR8 lncRNA with the defense response. AtR8 accumulation exhibited an inverse correlation with an accumulation of two WRKY genes (WRKY53/WRKY70) when plants were exposed to exogenous low SA concentrations (20 µM), infected with Pseudomonas syringae, or in the early stage of development. The highest AtR8 accumulation was observed 5 days after germination, at which time no WRKY53 or WRKY70 mRNA was detectable. The presence of low levels of SA resulted in a significant reduction of root length in atr8 seedlings, whereas wrky53 and wrky70 mutants exhibited the opposite phenotype. Taken together, AtR8 lncRNA participates in Pathogenesis-Related Proteins 1 (PR-1)-independent defense and root elongation, which are related to the SA response. The mutual regulation of AtR8 lncRNA and WRKY53/WRKY70 is mediated by Nonexpressor of Pathogenesis-Related Gene 1 (NPR1).

Evolution, Initiation, and Diversity in Early Plant Embryogenesis.

During embryogenesis in plants, cell identities are specified de novo, starting from a single cell. By combining imaging, genomic profiling, and genetics, principles of early plant development have been unraveled in the dicotyledonous plant Arabidopsis. A central emerging question, however, is how well zygotic embryogenesis in Arabidopsis reflects homologous processes in other plant species, including early diverging, non-flowering, and non-seed plants. Here, we consider plant embryogenesis with an emphasis on its evolutionary history, the diverse modes of its initiation, and the concepts in pattern formation among morphologically distinct plant groups. Furthermore, we explore challenges and future directions in plant embryogenesis research.

Natural depletion of histone H1 in sex cells causes DNA demethylation, heterochromatin decondensation and transposon activation

Transposable elements (TEs), the movement of which can damage the genome, are epigenetically silenced in eukaryotes. Intriguingly, TEs are activated in the sperm companion cell - vegetative cell (VC) - of the flowering plant Arabidopsis thaliana. However, the extent and mechanism of this activation are unknown. Here we show that about 100 heterochromatic TEs are activated in VCs, mostly by DEMETER-catalyzed DNA demethylation. We further demonstrate that DEMETER access to some of these TEs is permitted by the natural depletion of linker histone H1 in VCs. Ectopically expressed H1 suppresses TEs in VCs by reducing DNA demethylation and via a methylation-independent mechanism. We demonstrate that H1 is required for heterochromatin condensation in plant cells and show that H1 overexpression creates heterochromatic foci in the VC progenitor cell. Taken together, our results demonstrate that the natural depletion of H1 during male gametogenesis facilitates DEMETER-directed DNA demethylation, heterochromatin relaxation, and TE activation.

Using the sample maximum to estimate the parameters of the underlying distribution.

We propose novel estimators for the parameters of an exponential distribution and a normal distribution when the only known information is a sample of sample maxima; i.e., the known information consists of a sample of m values, each of which is the maximum of a sample of n independent random variables drawn from the underlying exponential or normal distribution. We analyze the accuracy and precision of the estimators using extreme value theory, as well as through simulations of the sampling distributions. For the exponential distribution, the estimator of the mean is unbiased and its variance decreases as either m or n increases. Likewise, for the normal distribution, we show that the estimator of the mean has negligible bias and the estimator of the variance is unbiased. While the variance of the estimators for the normal distribution decreases as m, the number of sample maxima, increases, the variance increases as n, the sample size over which the maximum is computed, increases. We apply our method to estimate the mean length of pollen tubes in the flowering plant Arabidopsis thaliana, where the known biological information fits our context of a sample of sample maxima.

RNA uridylation and decay in plants.

RNA uridylation consists of the untemplated addition of uridines at the 3' extremity of an RNA molecule. RNA uridylation is catalysed by terminal uridylyltransferases (TUTases), which form a subgroup of the terminal nucleotidyltransferase family, to which poly(A) polymerases also belong. The key role of RNA uridylation is to regulate RNA degradation in a variety of eukaryotes, including fission yeast, plants and animals. In plants, RNA uridylation has been mostly studied in two model species, the green algae Chlamydomonas reinhardtii and the flowering plant Arabidopsis thaliana Plant TUTases target a variety of RNA substrates, differing in size and function. These RNA substrates include microRNAs (miRNAs), small interfering silencing RNAs (siRNAs), ribosomal RNAs (rRNAs), messenger RNAs (mRNAs) and mRNA fragments generated during post-transcriptional gene silencing. Viral RNAs can also get uridylated during plant infection. We describe here the evolutionary history of plant TUTases and we summarize the diverse molecular functions of uridylation during RNA degradation processes in plants. We also outline key points of future research.This article is part of the theme issue '5' and 3' modifications controlling RNA degradation'.

Refinements to light sources used to analyze the chloroplast cold-avoidance response over the past century

ABSTRACTChloroplasts alter their subcellular positions in response to ambient light and temperature conditions. This well-characterized light-induced response, which was first described nearly 100 years ago, is regulated by the blue-light photoreceptor, phototropin. By contrast, the molecular mechanism of low temperature-induced chloroplast relocation (i.e., the cold-avoidance response) was unexplored until its discovery in the fern Adiantum capillus-veneris in 2008. Because this response is also regulated by phototropin, it was thought to occur in a blue light-dependent manner. However, until recently, the blue light dependency of this response could not be examined due to the lack of a stable light source under cold conditions. We recently refined the light source to precisely control light intensity under cold conditions. Using this light source, we observed the blue light dependency of the cold-avoidance response in the liverwort Marchantia polymorpha and the phototropin2-mediated cold-avoidance response in the flowering plant Arabidopsis thaliana. Thus, this mechanism is evolutionarily conserved among land plants.

Three-Dimensional Superresolution Imaging of the FtsZ Ring during Cell Division of the Cyanobacterium Prochlorococcus.

ABSTRACTSuperresolution imaging has revealed subcellular structures and protein interactions in many organisms. However, superresolution microscopy with lateral resolution better than 100 nm has not been achieved in photosynthetic cells due to the interference of a high-autofluorescence background. Here, we developed a photobleaching method to effectively reduce the autofluorescence of cyanobacterial and plant cells. We achieved lateral resolution of ~10 nm with stochastic optical reconstruction microscopy (STORM) in the sphere-shaped cyanobacterium Prochlorococcus and the flowering plant Arabidopsis thaliana. During the cell cycle of Prochlorococcus, we characterized the three-dimensional (3D) organization of the cell division protein FtsZ, which forms a ring structure at the division site and is important for cytokinesis of bacteria and chloroplasts. Although the FtsZ ring assembly process in rod-shaped bacteria has been studied extensively, it has rarely been studied in sphere-shaped bacteria. Similarly to rod-shaped bacteria, our results with Prochlorococcus also showed the assembly of FtsZ clusters into incomplete rings and then complete rings during cell division. Differently from rod-shaped bacteria, the FtsZ ring diameter was not found to decrease during Prochlorococcus cell division. We also discovered a novel double-Z-ring structure, which may be the Z rings of two daughter cells in a predivisional mother cell. Our results showed a quantitative picture of the in vivo Z ring organization of sphere-shaped bacteria.

A Molecular Framework for the Embryonic Initiation of Shoot Meristem Stem Cells

The establishment of pluripotent stem cells is a keyevent during plant and animal embryogenesis, but the underlying mechanisms remain enigmatic. We show that in the flowering plant Arabidopsis thaliana, expression of the shoot meristem stem cell marker CLV3 becomes detectable in transition stage embryos. Surprisingly, the key regulator of stem cell homeostasis WUSCHEL (WUS) is expressed but dispensable for stem cell initiation. Rather, the WUS paralog WOX2, a regulator of embryo patterning initiated in the zygote, functions in this process by shielding stem cell progenitors from differentiation. WOX2 upregulates HD-ZIP III transcription factors required for shoot identity and balances cytokinin versus auxin hormone pathways, revealing that classical plantlet regeneration procedures recapitulate the natural induction mechanism. Our findings link transcriptional regulation of early embryo patterning to hormonal control of stem cell initiation and suggest that similar strategies have evolved in plant and animal stem cell formation.

Araport11: a complete reannotation of the Arabidopsis thaliana reference genome.

The flowering plant Arabidopsis thaliana is a dicot model organism for research in many aspects of plant biology. A comprehensive annotation of its genome paves the way for understanding the functions and activities of all types of transcripts, including mRNA, the various classes of non-coding RNA, and small RNA. The TAIR10 annotation update had a profound impact on Arabidopsis research but was released more than 5years ago. Maintaining the accuracy of the annotation continues to be a prerequisite for future progress. Using an integrative annotation pipeline, we assembled tissue-specific RNA-Seq libraries from 113 datasets and constructed 48359 transcript models of protein-coding genes in eleven tissues. In addition, we annotated various classes of non-coding RNA including microRNA, long intergenic RNA, small nucleolar RNA, natural antisense transcript, small nuclear RNA, and small RNA using published datasets and in-house analytic results. Altogether, we identified 635 novel protein-coding genes, 508 novel transcribed regions, 5178 non-coding RNAs, and 35846 small RNA loci that were formerly unannotated. Analysis of the splicing events and RNA-Seq based expression profiles revealed the landscapes of gene structures, untranslated regions, and splicing activities to be more intricate than previously appreciated. Furthermore, we present 692 uniformly expressed housekeeping genes, 43% of whose human orthologs are also housekeeping genes. This updated Arabidopsis genome annotation with a substantially increased resolution of gene models will not only further our understanding of the biological processes of this plant model but also of other species.

Watching plants grow – a position paper on computer vision and Arabidopsis thaliana

The authors present a comprehensive overview of image processing and analysis work done to support research into the model flowering plant Arabidopsis thaliana. Beside the plant's importance in biological research, using image analysis to obtain experimental measurements of it is an interesting vision problem in its own right, involving the segmentation and analysis of sequences of images of objects whose shape varies between individual specimens and also changes over time. While useful measurements can be obtained by segmenting a whole plant from the background, they suggest that the increased range and precision of measurements made available by leaf‐level segmentation makes this a problem well worth solving. A variety of approaches have been tried by biologists as well as computer vision researchers. This is an interdisciplinary area and the computer vision community has an important contribution to make. They suggest that there is a need for publicly available datasets with ground truth annotations to enable the evaluation of new approaches and to support the building of training data for modern data‐driven computer vision approaches, which are those most likely to result in the kind of fully automated systems that will be of use to biologists.