Emergent Protective Organogenesis in Date Palms: A Morpho-Devo-Dynamic Adaptive Strategy during Early Development

The dual function of EMB1579 in transcription and splicing governs tissue patterning in the Arabidopsis root meristem

In the root meristem of Arabidopsis, stem cell maintenance depends on the coordinated action of transcription factor networks. The transcriptional regulator EMBRYO DEFECTIVE 1579 (EMB1579), a protein that forms nuclear condensates, regulates plant growth. However, the molecular mechanisms through which it functions in the root meristem remain largely unclear. Here, we show that EMB1579 is required for stem cell maintenance and proper cell division orientation. EMB1579 modulates the function of two root stem cell regulatory modules, PLETHORAs and SCARECROW-SHORT-ROOT, through a process involving transcriptional regulation and RNA splicing. We show that EMB1579 acts as a catalyst for stem cell gene expression, and its activity is fine-tuned by its physical association with RNA splicing factors. The formation of nuclear condensates is essential for EMB1579 function in the root meristem. Our findings reveal a mechanism by which EMB1579 regulates stem cell determinants in the root meristem and expand the understanding of gene regulation complexity in plant development.

Proteome changes during the germination and early seedling development of carnauba palm (Copernicia prunifera) under skotomorphogenic conditions

We analyze the proteome changes during the development of the carnauba palm (Copernicia prunifera) seedlings under skotomorphogenic conditions, by separating the embryo into its two components: haustorium (HA) and cotyledonary petiole (CP) and established the descriptive and quantitative proteomes of these tissues across four developmental stages. 5205 proteins were identified in HA and 6028 in CP. These proteomes are rich in proteins known to maintain the skotomorphogenic state, and in a complete set of proteins involved in cellular respiration and biosynthesis of secondary metabolites. The quantitative analysis employing a label-free approach revealed that 583 proteins in HA and 383 in CP were differentially abundant, with 251 proteins shared between the datasets. The results showed that HA participates in the digestion of food reserves present in HA itself and in the endosperm, acting as a conduit of nitrogen and carbon sources for the growing embryo axis. Among the differentially abundant proteins in the CP, we identified the presence of proteins from the cellular metabolism and proteins involved in the hydrolysis of food reserves such as starch and proteins. This indicates that the CP, in addition to the endosperm and HA, serves as a source of food reserves for the embryo axis. SIGNIFICANCE: Our results also reveal the differential regulation of specific proteins involved in reactive oxygen species scavenging, cell wall remodeling, respiratory metabolism, and protein repair in seeds and seedlings of C. prunifera. These findings have broad implications for understanding the energy metabolism that drives the transition from seed to seedling. For this study, we employed state-of-the-art proteomic techniques, including quantitative mass spectrometry and bioinformatic analysis, that allowed us to create a large dataset that will be a valuable resource for future research on the physiological and biochemical aspects of skotomorphogenesis, photomorphogenesis, and the transition between these states.

Microscopy and spatial-metabolomics identify tissue-specific metabolic pathways uncovering salinity and drought tolerance mechanisms in Avicennia marina and Phoenix dactylifera roots

In arid and semi-arid climates, native plants have developed unique strategies to survive challenging conditions. These adaptations often rely on molecular pathways that shape plant architecture to enhance their resilience. Date palms (Phoenix dactylifera) and mangroves (Avicennia marina) endure extreme heat and high salinity, yet the metabolic pathways underlying this resilience remain underexplored. Here, we integrate tissue imaging with spatial metabolomics to uncover shared and distinct adaptive features in these species. We found that mangrove roots accumulate suberin and lignin in meristematic tissues, this is unlike other plant species, where only the differentiation zones contain these compounds. Our metabolomic analysis shows that date palm roots are enriched in metabolites involved in amino acid biosynthesis, whereas compounds involved in lignin and suberin production were more abundant in mangrove roots. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) revealed tissue- and species-specific metabolite distributions in root tissues. We identified common osmoprotectants accumulating in the exodermis/epidermis of date palm and mangrove root meristems, along with a unique metabolite highly abundant in the inner cortex of date palm roots. These findings provide valuable insights into stress adaptation pathways and highlight key tissue types involved in root stress response.

How to Cope With Stress in the Desert-The Date Palm Approach

Increasing desertification constitutes a global environmental problem, mainly driven by climate change and inappropriate land-use that limits agriculture, forestry and human colonization. The selection of suitable plant species to mitigate desertification is particularly challenging, as it usually requires simultaneous counteraction against a whole set of unfavourable environmental conditions, including heat, drought, high tropospheric ozone and salinity. It therefore seems useful to identify the survival strategies of plants native in desert environments. Date palm constitutes a plant species native in desert environments and cultivated worldwide in arid regions that have been studied intensively for stress defence during the last decade. The present review summarizes the current state of biochemical stress defence mechanisms including avoidance, osmotic and metabolic adjustments and reactive oxygen species scavenging, addresses whole-plant regulations and trade-off between stress compensation/defence and growth of date palms. The review advances our knowledge about how this typical desert species copes with both individual and multiple environmental stresses at the cellular to the whole-plant level, and identifies areas of future research required to fully understand the strategies of this plant species to survive in the desert, thereby contributing to efforts for the mitigation of climate change and desertification.

Rooting for survival: how plants tackle a challenging environment through a diversity of root forms and functions

The current climate crisis has global impacts and will affect the physiology of plants across every continent. Ensuring resilience of our agricultural and natural ecosystems to the environmental stresses imposed by climate change will require molecular insight into the adaptations employed by a diverse array of plants. However, most current studies continue to focus on a limited set of model species or crops. Root systems are particularly understudied even though their functions in water and nutrient uptake are likely pivotal for plant stress resilience and sustainable agriculture. In this review, we highlight anatomical adaptations in roots that enable plant survival in different ecological niches. We then present the current state of knowledge for the molecular underpinnings of these adaptations. Finally, we identify areas where future research using a biodiversity approach can fill knowledge gaps necessary for the development of climate-resilient crops of the future.

Developmental and Genetic Aspects of Desert Crops

Deserts are hostile environments to plant life due to exposure to abiotic stresses, including high temperature, heat, high light, low water availability, and poor soil quality. Desert plants have evolved to cope with these stresses, and for thousands of years humans have used these plants as sources of food, fiber, and medicine. Due to desertification, the amount of arable land is reduced every year; hence, the usage of these species as substitutes for some crops might become one of the solutions for food production and land remediation. Additionally, increasing our understanding of how these plants have adapted to their environment could aid in the generation of more resistant staple crops. In this review, we examine three desert plant species and discuss their developmental aspects, physiological adaptations, and genetic diversity and the related genomic resources available to date. We also address major environmental challenges and threats faced by these species as well as their potential use for improving food security through stimulating stress resistance in crops.

Three-dimensional reconstruction and multiomics analysis reveal a unique pattern of embryogenesis in Ginkgo biloba

Ginkgo (Ginkgo biloba L.) is one of the earliest extant species in seed plant phylogeny. Embryo development patterns can provide fundamental evidence for the origin, evolution, and adaptation of seeds. However, the architectural and morphological dynamics during embryogenesis in G. biloba remain elusive. Herein, we obtained over 2,200 visual slices from 3 stages of embryo development using micro-computed tomography imaging with improved staining methods. Based on 3-dimensional (3D) spatiotemporal pattern analysis, we found that a shoot apical meristem with 7 highly differentiated leaf primordia, including apical and axillary leaf buds, is present in mature Ginkgo embryos. 3D rendering from the front, top, and side views showed 2 separate transport systems of tracheids located in the hypocotyl and cotyledon, representing a unique pattern of embryogenesis. Furthermore, the morphological dynamic analysis of secretory cavities indicated their strong association with cotyledons during development. In addition, we identified genes GbLBD25a (lateral organ boundaries domain 25a), GbCESA2a (cellulose synthase 2a), GbMYB74c (myeloblastosis 74c), GbPIN2 (PIN-FORMED 2) associated with vascular development regulation, and GbWRKY1 (WRKYGOK 1), GbbHLH12a (basic helix-loop-helix 12a), and GbJAZ4 (jasmonate zim-domain 4) potentially involved in the formation of secretory cavities. Moreover, we found that flavonoid accumulation in mature embryos could enhance postgerminative growth and seedling establishment in harsh environments. Our 3D spatial reconstruction technique combined with multiomics analysis opens avenues for investigating developmental architecture and molecular mechanisms during embryogenesis and lays the foundation for evolutionary studies of embryo development and maturation.

Date palm transcriptome analysis provides new insights on changes in response to high salt stress of colonized roots with the endophytic fungus Piriformospora indica

Salinity is a significant threat that causes considerable yield losses in date palm. The root endophytic fungus Piriformospora indica has proven effective in providing salt stress tolerance to host plants. However, the underlying molecular mechanism facilitating the date palm's response to P. indica inoculation, and its involvement in the salt stress tolerance, remains unknown. In this study, the colonization of P. indica on date palm seedlings exposed to saline conditions was observed through confocal microscopy, and its impact on gene expressions was evaluated using the transcriptomic analysis. Our findings show that P. indica colonization reinforced the cortical cells, prevented them from plasmolysis and cell death under salinity. The RNAseq analysis produced clean reads ranging from 62,040,451 to 3,652,095 across the treatment groups, successfully assembling into 30,600 annotated genes. Out of them, the number of differentially expressed genes (DEGs) varied across the treatments: i.e., 2523, 2031, and 1936 DEGs were upregulated, while 2323, 959, and 3546 were downregulated in Salt, Fungi, and Fungi+Salt groups, respectively. Furthermore, principal component analysis based on transcriptome profiles revealed discrete clustering of samples from different treatment groups. KEGG and GO pathways enrichment analysis highlighted variation in the number and types of enriched pathways among the treatments. Our study indicated variations in gene expression related to plant hormone biosynthesis and signal transduction (auxin, abscisic acid, gibberellin, and ethylene), ABC transporters, sodium/hydrogen exchanger, cation HKT transporter, transcription factors such as WRKY and MYBs, and the plant immune system (lipoxygenase and jasmonate) of the date palm seedlings. By characterizing the transcriptome of date palm roots under salt stress and with colonization of P. indica, the present findings provide valuable perspectives on the molecular mechanisms responsible for inducing salinity stress tolerance in plants.

A framework for date palm (Phoenix dactylifera L.) tissue regeneration and stable transformation

The date palm is a resilient, socioeconomically valuable desert fruit tree renowned for its heat, drought, and salinity tolerance. Date palm fruits are rich in nutrients and antioxidants, and their beneficial health properties can mitigate current and future food security challenges. However, it is challenging to improve date palm production through conventional breeding methods due to its slow growth. Date palm seeds do not produce true-to-type progeny, and commercial propagation relies on direct organogenesis from maternal tissue. Consequently, numerous economically important and valuable cultivars are lost due to tissue recalcitrance and challenges in inducing cell dedifferentiation and regeneration. Moreover, genetic engineering of date palms is currently impossible due to the lack of a stable genetic transformation protocol. This hampers the development of genetic resources in date palms. This study established a tissue culture pipeline and a genetic transformation protocol for various commercially important date palm cultivars. We used the non-invasive visual reporter RUBY and four morphogenic regulators to validate and improve date palm transformation potential. We found that the date palm BABY-BOOM (PdBBM) and the WOUND INDUCED DEDIFFERENTIATION (PdWIND1) enhanced transformation efficacy. We show that PdBBM can induce embryogenesis in hormone-free media and regenerate roots and shoots in recalcitrant varieties. On the other hand, PdWIND1 maintained embryogenic cells in their undifferentiated state. Our study provides a foundation for genetically improving date palms and a potential solution for preserving economically valuable varieties.

Disruption of the rice 4-DEOXYOROBANCHOL HYDROXYLASE unravels specific functions of canonical strigolactones

Strigolactones (SLs) regulate many developmental processes, including shoot-branching/tillering, and mediate rhizospheric interactions. SLs originate from carlactone (CL) and are structurally diverse, divided into a canonical and a noncanonical subfamily. Rice contains two canonical SLs, 4-deoxyorobanchol (4DO) and orobanchol (Oro), which are common in different plant species. The cytochrome P450 OsMAX1-900 forms 4DO from CL through repeated oxygenation and ring closure, while the homologous enzyme OsMAX1-1400 hydroxylates 4DO into Oro. To better understand the biological function of 4DO and Oro, we generated CRISPR/Cas9 mutants disrupted in OsMAX1-1400 or in both OsMAX1-900 and OsMAX1-1400. The loss of OsMAX1-1400 activity led to a complete lack of Oro and an accumulation of its precursor 4DO. Moreover, Os1400 mutants showed shorter plant height, panicle and panicle base length, but no tillering phenotype. Hormone quantification and transcriptome analysis of Os1400 mutants revealed elevated auxin levels and changes in the expression of auxin-related, as well as of SL biosynthetic genes. Interestingly, the Os900/1400 double mutant lacking both Oro and 4DO did not show the observed Os1400 architectural phenotypes, indicating their being a result of 4DO accumulation. Treatment of wild-type plants with 4DO confirmed this assumption. A comparison of the Striga seed germinating activity and the mycorrhization of Os900, Os900/1400, and Os1400 loss-of-function mutants demonstrated that the germination activity positively correlates with 4DO content while disrupting OsMAX1-1400 has a negative impact on mycorrhizal symbiosis. Taken together, our paper deciphers the biological function of canonical SLs in rice and reveals their particular contributions to establishing architecture and rhizospheric communications.

Kalaf Y, M. Abd A. Anatomical study of the roots of seven varieties of date palm (Phoenix dactylifera L.)

This study was conducted at one of the private orchards to determine the variety through the anatomical characteristics of the roots; three palm trees were selected for each variety, identical, 15-18 years of age. The anatomical characteristics of the roots of seven date palm varieties were studied. The studied traits were circumferential circle diameter, phloem bundle length, xylem bundle length, next xylem, epidermis, sub-epidermal, fibrous bundle, cortex, and the diameter of parenchymal cells. Results show that the studied varieties differed in the studied anatomical characteristics. The Khadrawi variety was significantly superior in the characteristic of the surrounding circle diameter compared to the rest of the studied varieties, The Barhi variety was significant in the cortex and phloem bundle length, The Asabee Al-Aroos variety was distinguished in the characteristic of epidermis thickness, and the lowest values were in the variety Halawi. The Halawi variety was distinguished by the thickness of the sub-epidermal area, and the lowest values were in the Barhi variety. Keywords: Anatomical study, roots, seven varieties, date palm (Phoenix dactylifera L.)

(Don't) Look Up!: Is short-root just a short-root plant?

SHORT-ROOT (SHR) is a mobile transcription factor that plays important roles in ground tissue patterning, stem cell niche specification and maintenance, and vascular development in Arabidopsis roots. Although mRNA and protein of SHR are also found in hypocotyls, inflorescence stems, and leaves, its role in the above-ground organs has been less explored. In most developmental cases, SHR, together with its partner SCARECROW (SCR), regulates the expression of downstream target genes in controlling formative and proliferative cell divisions. Accumulating evidence on the regulatory role of SHR in shoots suggests that SHR may also play key roles in the above-ground organs. Interestingly, recent work has provided new evidence that SHR is also required for cell elongation in the hypocotyl of the etiolated seedling. This suggests that the novel roles of SHR and SHR-mediated regulatory networks can be found in shoots. Furthermore, comparative research on SHR function in roots and shoots will broaden and deepen our understanding of plant growth and development.

Transcriptional analysis of Ceratopteris richardii young sporophyte reveals conservation of stem cell factors in the root apical meristem

Gene expression in roots has been assessed in different plant species in studies ranging from complete organs to specific cell layers, and more recently at the single cell level. While certain genes or functional categories are expressed in the root of all or most plant species, lineage-specific genes have also been discovered. An increasing amount of transcriptomic data is available for angiosperms, while a limited amount of data is available for ferns, and few studies have focused on fern roots. Here, we present a de novo transcriptome assembly from three different parts of the Ceratopteris richardii young sporophyte. Differential gene expression analysis of the root tip transcriptional program showed an enrichment of functional categories related to histogenesis and cell division, indicating an active apical meristem. Analysis of a diverse set of orthologous genes revealed conserved expression in the root meristem, suggesting a preserved role for different developmental roles in this tissue, including stem cell maintenance. The reconstruction of evolutionary trajectories for ground tissue specification genes suggests a high degree of conservation in vascular plants, but not for genes involved in root cap development, showing that certain genes are absent in Ceratopteris or have intricate evolutionary paths difficult to track. Overall, our results suggest different processes of conservation and divergence of genes involved in root development.

A PLETHORA/PIN-FORMED/auxin network mediates prehaustorium formation in the parasitic plant Striga hermonthica

The parasitic plant Striga (Striga hermonthica) invades the host root through the formation of a haustorium and has detrimental impacts on cereal crops. The haustorium results from the prehaustorium, which is derived directly from the differentiation of the Striga radicle. The molecular mechanisms leading to radicle differentiation shortly after germination remain unclear. In this study, we determined the developmental programs that regulate terminal prehaustorium formation in S. hermonthica at cellular resolution. We showed that shortly after germination, cells in the root meristem undergo multiplanar divisions. During growth, the meristematic activity declines and associates with reduced expression of the stem cell regulator PLETHORA1 and the cell cycle genes CYCLINB1 and HISTONE H4. We also observed a basal localization of the PIN-FORMED (PIN) proteins and a decrease in auxin levels in the meristem. Using the structural layout of the root meristem and the polarity of outer-membrane PIN proteins, we constructed a mathematical model of auxin transport that explains the auxin distribution patterns observed during S. hermonthica root growth. Our results reveal a fundamental molecular and cellular framework governing the switch of S. hermonthica roots to form the invasive prehaustoria.

Evaluation of the Biostimulant Activity of Zaxinone Mimics (MiZax) in Crop Plants

Global food security is a critical concern that needs practical solutions to feed the expanding human population. A promising approach is the employment of biostimulants to increase crop production. Biostimulants include compounds that boost plant growth. Recently, mimics of zaxinone (MiZax) were shown to have a promising growth-promoting effect in rice (Oryza sativa). In this study, we investigated the effect of MiZax on the growth and yield of three dicot horticultural plants, namely, tomato (Solanum lycopersicum), capsicum (Capsicum annuum), and squash (Cucurbita pepo) in different growth environments, as well as on the growth and development of the monocot date palm (Phoenix dactylifera), an important crop in the Middle East. The application of MiZax significantly enhanced plant height, flower, and branch numbers, fruit size, and total fruit yield in independent field trials from 2020 to 2021. Importantly, the amount of applied MiZax was far less than that used with the commercial compound humic acid, a widely used biostimulant in horticulture. Our results indicate that MiZax have significant application potential to improve the performance and productivity of horticultural crops.

Ground tissue circuitry regulates organ complexity in maize and Setaria

[Figure: see text].

Multi-omics approaches explain the growth-promoting effect of the apocarotenoid growth regulator zaxinone in rice

The apocarotenoid zaxinone promotes growth and suppresses strigolactone biosynthesis in rice. To shed light on the mechanisms underlying its growth-promoting effect, we employed a combined omics approach integrating transcriptomics and metabolomics analysis of rice seedlings treated with zaxinone, and determined the resulting changes at the cellular and hormonal levels. Metabolites as well as transcripts analysis demonstrate that zaxinone application increased sugar content and triggered glycolysis, the tricarboxylic acid cycle and other sugar-related metabolic processes in rice roots. In addition, zaxinone treatment led to an increased root starch content and induced glycosylation of cytokinins. The transcriptomic, metabolic and hormonal changes were accompanied by striking alterations of roots at cellular level, which showed an increase in apex length, diameter, and the number of cells and cortex cell layers. Remarkably, zaxinone did not affect the metabolism of roots in a strigolactone deficient mutant, suggesting an essential role of strigolactone in the zaxinone growth-promoting activity. Taken together, our results unravel zaxinone as a global regulator of the transcriptome and metabolome, as well as of hormonal and cellular composition of rice roots. Moreover, they suggest that zaxinone promotes rice growth most likely by increasing sugar uptake and metabolism, and reinforce the potential of this compound in increasing rice performance.

Wang et al. report zaxinone as a global regulator of the transcriptome and metabolome, as well as of hormonal and cellular composition of rice roots. This study shows that zaxinone promotes rice growth by enhancing root sugar uptake and metabolism and modulation of cytokinin content, indicating the potential application of this compound in increasing rice performance.

Rooting in the Desert: A Developmental Overview on Desert Plants

Plants, as sessile organisms, have evolved a remarkable developmental plasticity to cope with their changing environment. When growing in hostile desert conditions, plants have to grow and thrive in heat and drought. This review discusses how desert plants have adapted their root system architecture (RSA) to cope with scarce water availability and poor nutrient availability in the desert soil. First, we describe how some species can survive by developing deep tap roots to access the groundwater while others produce shallow roots to exploit the short rain seasons and unpredictable rainfalls. Then, we discuss how desert plants have evolved unique developmental programs like having determinate meristems in the case of cacti while forming a branched and compact root system that allows efficient water uptake during wet periods. The remote germination mechanism in date palms is another example of developmental adaptation to survive in the dry and hot desert surface. Date palms have also designed non-gravitropic secondary roots, termed pneumatophores, to maximize water and nutrient uptake. Next, we highlight the distinct anatomical features developed by desert species in response to drought like narrow vessels, high tissue suberization, and air spaces within the root cortex tissue. Finally, we discuss the beneficial impact of the microbiome in promoting root growth in desert conditions and how these characteristics can be exploited to engineer resilient crops with a greater ability to deal with salinity induced by irrigation and with the increasing drought caused by global warming.

Plant multiscale networks: charting plant connectivity by multi-level analysis and imaging techniques

In multicellular and even single-celled organisms, individual components are interconnected at multiscale levels to produce enormously complex biological networks that help these systems maintain homeostasis for development and environmental adaptation. Systems biology studies initially adopted network analysis to explore how relationships between individual components give rise to complex biological processes. Network analysis has been applied to dissect the complex connectivity of mammalian brains across different scales in time and space in The Human Brain Project. In plant science, network analysis has similarly been applied to study the connectivity of plant components at the molecular, subcellular, cellular, organic, and organism levels. Analysis of these multiscale networks contributes to our understanding of how genotype determines phenotype. In this review, we summarized the theoretical framework of plant multiscale networks and introduced studies investigating plant networks by various experimental and computational modalities. We next discussed the currently available analytic methodologies and multi-level imaging techniques used to map multiscale networks in plants. Finally, we highlighted some of the technical challenges and key questions remaining to be addressed in this emerging field.

PYL8 ABA receptors of Phoenix dactylifera play a crucial role in response to abiotic stress and are stabilized by ABA

The identification of those prevalent abscisic acid (ABA) receptors and molecular mechanisms that trigger drought adaptation in crops well adapted to harsh conditions such as date palm (Phoenix dactylifera, Pd) sheds light on plant-environment interactions. We reveal that PdPYL8-like receptors are predominantly expressed under abiotic stress, with Pd27 being the most expressed receptor in date palm. Therefore, subfamily I PdPYL8-like receptors have been selected for ABA signaling during abiotic stress response in this crop. Biochemical characterization of PdPYL8-like and PdPYL1-like receptors revealed receptor- and ABA-dependent inhibition of PP2Cs, which triggers activation of the pRD29B-LUC reporter in response to ABA. PdPYLs efficiently abolish PP2C-mediated repression of ABA signaling, but loss of the Trp lock in the seed-specific AHG1-like phosphatase PdPP2C79 markedly impairs its inhibition by ABA receptors. Characterization of Arabidopsis transgenic plants that express PdPYLs shows enhanced ABA signaling in seed, root, and guard cells. Specifically, Pd27-overexpressing plants showed lower ABA content and were more efficient than the wild type in lowering transpiration at negative soil water potential, leading to enhanced drought tolerance. Finally, PdPYL8-like receptors accumulate after ABA treatment, which suggests that ABA-induced stabilization of these receptors operates in date palm for efficient boosting of ABA signaling in response to abiotic stress.

Prospects for the Study and Improvement of Abiotic Stress Tolerance in Date Palms in the Post-genomics Era

Date palm (Phoenix dactylifera L.) is a socio-economically important crop in the Middle East and North Africa and a major contributor to food security in arid regions of the world. P. dactylifera is both drought and salt tolerant, but recent water shortages and increases in groundwater and soil salinity have threatened the continued productivity of the crop. Recent studies of date palm have begun to elucidate the physiological mechanisms of abiotic stress tolerance and the genes and biochemical pathways that control the response to these stresses. Here we review recent studies on tolerance of date palm to salinity and drought stress, the role of the soil and root microbiomes in abiotic stress tolerance, and highlight recent findings of omic-type studies. We present a perspective on future research of abiotic stress in date palm that includes improving existing genome resources, application of genetic mapping to determine the genetic basis of variation in tolerances among cultivars, and adoption of gene-editing technologies to the study of abiotic stress in date palms. Development of necessary resources and application of the proposed methods will provide a foundation for future breeders and genetic engineers aiming to develop more stress-tolerant cultivars of date palm.

Vibratome Sectioning and Clearing for Easing Studies of Cassava Embryo Formation

This work describes the application of clearing on vibratome sections to study the embryo formation in cassava. This procedure provides high-resolution images and reduces significantly the number of sections that need to be analyzed per ovule. This methodology was instrumental for the development of the protocol for embryo rescue in cassava. It has been also applied to monitor the embryo formation response when optimizing seed setting from regular and broad crosses for cassava breeding. Broad crosses between cassava and castor bean (incompatible-euphorbiaceae species) were made aiming to induce doubled haploids through the elimination of the incompatible-male parent genome as done in cereals. Castor bean is widely available and provides continues supply of pollen. Our results suggest that this methodology is easy and effective to assess the response of hundreds of cassava ovules pollinated with castor bean pollen, allowing the identification of multicellular structures in the embryo sac without apparent formation of endosperm. The protocol is also useful when developing and optimizing a methodology to induce doubled haploids in cassava via gynogenesis or from ovules pollinated with irradiated cassava pollen.