Revolutions in agriculture chart a course for targeted breeding of old and new crops

The diversification of the shoot branching system: A quantitative and comparative perspective in meristem determinacy

Reiterative shoot branching largely defines important yield components of crops and is essentially controlled by programs that direct the initiation, dormancy release, and differentiation of meristems in the axils of leaves. Here, we focus on meristem determinacy, defining the number of reiterations that shape the shoot architectures and exhibit enormous diversity in a wide range of species. The meristem determinacy per se is hierarchically complex and context-dependent for the successively emerged meristems, representing a crucial mechanism in shaping the complexity of the shoot branching. In addition, we have highlighted that two key components of axillary meristem developmental programs may have been co-opted in controlling flower/ear number of an axillary inflorescence in legumes/maize, hinting at the diversification of axillary-meristem-patterning programs in different lineages. This begs the question how axillary meristem patterning programs may have diversified during plant evolution and hence helped shape the rich variation in shoot branching systems.

Allelic variation of TaABI5-A4 significantly affects seed dormancy in bread wheat

KEY MESSAGE

We identified a pivotal transcription factor TaABI5-A4 that is significantly associated with pre-harvest sprouting in wheat; its function in regulating seed dormancy was confirmed in transgenic rice. ABI5 is a critical transcription factor in regulation of crop seed maturation, dormancy, germination, and post-germination. Sixteen copies of homologous sequences of ABI5 were identified in Chinese wheat line Zhou 8425B. Cultivars of two haplotypes TaABI5-A4a and TaABI5-A4b showed significantly different seed dormancies. Based on two SNPs between the sequences of TaABI5-A4a and TaABI5-A4b, two complementary dominant sequence-tagged site (STS) markers were developed and validated in a natural population of 103 Chinese wheat cultivars and advanced lines and 200 recombinant inbred lines (RILs) derived from the Yangxiaomai/Zhongyou 9507 cross; the STS markers can be used efficiently and reliably to evaluate the dormancy of wheat seeds. The transcription level of TaABI5-A4b was significantly increased in TaABI5-A4a-GFP transgenic rice lines compared with that in TaABI5-A4b-GFP. The average seed germination index of TaABI5-A4a-GFP transgenic rice lines was significantly lower than those of TaABI5-A4b-GFP. In addition, seeds of TaABI5-A4a-GFP transgenic lines had higher ABA sensitivity and endogenous ABA content, lower endogenous GA content and plant height, and thicker stem internodes than those of TaABI5-A4b-GFP. Allelic variation of TaABI5-A4-affected wheat seed dormancy and the gene function was confirmed in transgenic rice. The transgenic rice lines of TaABI5-A4a and TaABI5-A4b had significantly different sensitivities to ABA and contents of endogenous ABA and GA in mature seeds, thereby influencing the seed dormancy, plant height, and stem internode length and diameter.

Strawberry phenotypic plasticity in flowering time is driven by the interaction between genetic loci and temperature

Flowering time (FT), which determines when fruits or seeds can be harvested, is subject to phenotypic plasticity, that is, the ability of a genotype to display different phenotypes in response to environmental variation. Here, we investigated how the environment affects the genetic architecture of FT in cultivated strawberry (Fragaria × ananassa) and modifies its quantitative trait locus (QTL) effects. To this end, we used a bi-parental segregating population grown for 2 years at widely divergent latitudes (five European countries) and combined climatic variables with genomic data (Affymetrix SNP array). Examination, using different phenological models, of the response of FT to photoperiod, temperature, and global radiation indicated that temperature is the main driver of FT in strawberry. We next characterized in the segregating population the phenotypic plasticity of FT by using three statistical approaches that generated plasticity parameters including reaction norm parameters. We detected 25 FT QTLs summarized as 10 unique QTLs. Mean values and plasticity parameter QTLs were co-localized in three of them, including the major 6D_M QTL whose effect is strongly modulated by temperature. The design and validation of a genetic marker for the 6D_M QTL offers great potential for breeding programs, for example selecting early-flowering strawberry varieties well adapted to different environmental conditions.

Biological macromolecules mediated by environmental signals affect flowering regulation in plants: A comprehensive review

Flowering time is a crucial developmental stage in the life cycle of plants, as it determines the reproductive success and overall fitness of the organism. The precise regulation of flowering time is influenced by various internal and external factors, including genetic, environmental, and hormonal cues. This review provided a comprehensive overview of the molecular mechanisms and regulatory pathways of biological macromolecules (e.g. proteins and phytohormone) and environmental factors (e.g. light and temperature) involved in the control of flowering time in plants. We discussed the key proteins and signaling pathways that govern the transition from vegetative growth to reproductive development, highlighting the intricate interplay between genetic networks, environmental cues, and phytohormone signaling. Additionally, we explored the impact of flowering time regulation on plant adaptation, crop productivity, and agricultural practices. Moreover, we summarized the similarities and differences of flowering mechanisms between annual and perennial plants. Understanding the mechanisms underlying flowering time control is not only essential for fundamental plant biology research but also holds great potential for crop improvement and sustainable agriculture.

Arabidopsis and maize terminator strength is determined by GC content, polyadenylation motifs and cleavage probability

The 3' end of a gene, often called a terminator, modulates mRNA stability, localization, translation, and polyadenylation. Here, we adapted Plant STARR-seq, a massively parallel reporter assay, to measure the activity of over 50,000 terminators from the plants Arabidopsis thaliana and Zea mays. We characterize thousands of plant terminators, including many that outperform bacterial terminators commonly used in plants. Terminator activity is species-specific, differing in tobacco leaf and maize protoplast assays. While recapitulating known biology, our results reveal the relative contributions of polyadenylation motifs to terminator strength. We built a computational model to predict terminator strength and used it to conduct in silico evolution that generated optimized synthetic terminators. Additionally, we discover alternative polyadenylation sites across tens of thousands of terminators; however, the strongest terminators tend to have a dominant cleavage site. Our results establish features of plant terminator function and identify strong naturally occurring and synthetic terminators.

An orchestrated ethylene-gibberellin signaling cascade contributes to mesocotyl elongation and emergence of rice direct seeding

A mechanized direct seeding of rice with less labor and water usage, has been widely adopted. However, this approach requires varieties that exhibit uniform seedling emergence. Mesocotyl elongation (ME) offers the main drive of fast emergence of rice seedlings from soils; nevertheless, its genetic basis remains unknown. Here, we identify a major rice quantitative trait locus Mesocotyl Elongation1 (qME1), an allele of the Green Revolution gene Semi-Dwarf1 (SD1), encoding GA20-oxidase for gibberellin (GA) biosynthesis. ME1 expression is strongly induced by soil depth and ethylene. When rice grains are direct-seeded in soils, the ethylene core signaling factor OsEIL1 directly promotes ME1 transcription, accelerating bioactive GA biosynthesis. The GAs further degrade the DELLA protein SLENDER RICE 1 (SLR1), alleviating its inhibition of rice PHYTOCHROME-INTERACTING FACTOR-LIKE13 (OsPIL13) to activate the downstream expansion gene OsEXPA4 and ultimately promote rice seedling ME and emergence. The ancient traits of long mesocotyl and strong emergence ability in wild rice and landrace were gradually lost in company with the Green Revolution dwarf breeding process, and an elite ME1-R allele (D349H) is found in some modern Geng varieties (long mesocotyl lengths) in northern China, which can be used in the direct seeding and dwarf breeding of Geng varieties. Furthermore, the ectopic and high expression of ME1 driven by mesocotyl-specific promoters resulted in rice plants that could be direct-seeded without obvious plant architecture or yield penalties. Collectively, we reveal the molecular mechanism of rice ME, and provide useful information for breeding new Green Revolution varieties with long mesocotyl suitable for direct-seeding practice.

Understanding plant-soil interactions underpins enhanced sustainability of crop production

The Green Revolution transformed agriculture with high-yielding, stress-resistant varieties. However, the urgent need for more sustainable agricultural development presents new challenges: increasing crop yield, improving nutritional quality, and enhancing resource-use efficiency. Soil plays a vital role in crop-production systems and ecosystem services, providing water, nutrients, and physical anchorage for crop growth. Despite advancements in plant and soil sciences, our understanding of belowground plant-soil interactions, which impact both crop performance and soil health, remains limited. Here, we argue that a lack of understanding of these plant-soil interactions hinders sustainable crop production. We propose that targeted engineering of crops and soils can provide a fresh approach to achieve higher yields, more efficient sustainable crop production, and improved soil health.

Identification and functional characterization of conserved cis-regulatory elements responsible for early fruit development in cucurbit crops

A number of cis-regulatory elements (CREs) conserved during evolution have been found to be responsible for phenotypic novelty and variation. Cucurbit crops such as cucumber (Cucumis sativus), watermelon (Citrullus lanatus), melon (Cucumis melo), and squash (Cucurbita maxima) develop fruits from an inferior ovary and share some similar biological processes during fruit development. Whether conserved regulatory sequences play critical roles in fruit development of cucurbit crops remains to be explored. In six well-studied cucurbit species, we identified 392,438 conserved noncoding sequences (CNSs), including 82,756 that are specific to cucurbits, by comparative genomics. Genome-wide profiling of accessible chromatin regions (ACRs) and gene expression patterns mapped 20,865 to 43,204 ACRs and their potential target genes for two fruit tissues at two key developmental stages in six cucurbits. Integrated analysis of CNSs and ACRs revealed 4,431 syntenic orthologous CNSs, including 1,687 cucurbit-specific CNSs that overlap with ACRs that are present in all six cucurbit crops and that may regulate the expression of 757 adjacent orthologous genes. CRISPR mutations targeting two CNSs present in the 1,687 cucurbit-specific sequences resulted in substantially altered fruit shape and gene expression patterns of adjacent NAC1 (NAM, ATAF1/2, and CUC2) and EXT-like (EXTENSIN-like) genes, validating the regulatory roles of these CNSs in fruit development. These results not only provide a number of target CREs for cucurbit crop improvement, but also provide insight into the roles of CREs in plant biology and during evolution.

Enhancing Yield and Improving Grain Quality in Japonica Rice: Targeted EHD1 Editing via CRISPR-Cas9 in Low-Latitude Adaptation

The "Indica to Japonica" initiative in China focuses on adapting Japonica rice varieties from the northeast to the unique photoperiod and temperature conditions of lower latitudes. While breeders can select varieties for their adaptability, the sensitivity to light and temperature often complicates and prolongs the process. Addressing the challenge of cultivating high-yield, superior-quality Japonica rice over expanded latitudinal ranges swiftly, in the face of these sensitivities, is critical. Our approach harnesses the CRISPR-Cas9 technology to edit the EHD1 gene in the premium northeastern Japonica cultivars Jiyuanxiang 1 and Yinongxiang 12, which are distinguished by their exceptional grain quality-increased head rice rates, gel consistency, and reduced chalkiness and amylose content. Field trials showed that these new ehd1 mutants not only surpass the wild types in yield when grown at low latitudes but also retain the desirable traits of their progenitors. Additionally, we found that disabling Ehd1 boosts the activity of Hd3a and RFT1, postponing flowering by approximately one month in the ehd1 mutants. This research presents a viable strategy for the accelerated breeding of elite northeastern Japonica rice by integrating genomic insights with gene-editing techniques suitable for low-latitude cultivation.

The Function of Florigen in the Vegetative-to-Reproductive Phase Transition in and around the Shoot Apical Meristem

Plants undergo a series of developmental phases throughout their life-cycle, each characterized by specific processes. Three critical features distinguish these phases: the arrangement of primordia (phyllotaxis), the timing of their differentiation (plastochron) and the characteristics of the lateral organs and axillary meristems. Identifying the unique molecular features of each phase, determining the molecular triggers that cause transitions and understanding the molecular mechanisms underlying these transitions are keys to gleaning a complete understanding of plant development. During the vegetative phase, the shoot apical meristem (SAM) facilitates continuous leaf and stem formation, with leaf development as the hallmark. The transition to the reproductive phase induces significant changes in these processes, driven mainly by the protein FT (FLOWERING LOCUS T) in Arabidopsis and proteins encoded by FT orthologs, which are specified as 'florigen'. These proteins are synthesized in leaves and transported to the SAM, and act as the primary flowering signal, although its impact varies among species. Within the SAM, florigen integrates with other signals, culminating in developmental changes. This review explores the central question of how florigen induces developmental phase transition in the SAM. Future research may combine phase transition studies, potentially revealing the florigen-induced developmental phase transition in the SAM.

Major quality regulation network of flavonoid synthesis governing the bioactivity of black wolfberry

Black wolfberry (Lycium ruthenicum Murr.) contains various bioactive metabolites represented by flavonoids, which are quite different among production regions. However, the underlying regulation mechanism of flavonoid biosynthesis governing the bioactivity of black wolfberry remains unclear. Presently, we compared the bioactivity of black wolfberry from five production regions. Multi-omics were performed to construct the regulation network associated with the fruit bioactivity. The detailed regulation mechanisms were identified using genetic and molecular methods. Typically, Qinghai (QH) fruit exhibited higher antioxidant and anti-inflammatory activities. The higher medicinal activity of QH fruit was closely associated with the accumulation of eight flavonoids, especially Kaempferol-3-O-rutinoside (K3R) and Quercetin-3-O-rutinoside (rutin). Flavonoid biosynthesis was found to be more active in QH fruit, and the upregulation of LrFLS, LrCHS, LrF3H and LrCYP75B1 caused the accumulation of K3R and rutin, leading to high medicinal bioactivities of black wolfberry. Importantly, transcription factor LrMYB94 was found to regulate LrFLS, LrCHS and LrF3H, while LrWRKY32 directly triggered LrCYP75B1 expression. Moreover, LrMYB94 interacted with LrWRKY32 to promote LrWRKY32-regulated LrCYP75B1 expression and rutin synthesis in black wolfberry. Transgenic black wolfberry overexpressing LrMYB94/LrWRKY32 contained higher levels of K3R and rutin, and exhibited high medicinal bioactivities. Importantly, the LrMYB94/LrWRKY32-regulated flavonoid biosynthesis was light-responsive, showing the importance of light intensity for the medicinal quality of black wolfberry. Overall, our results elucidated the regulation mechanisms of K3R and rutin synthesis, providing the basis for the genetic breeding of high-quality black wolfberry.

Technology-enabled great leap in deciphering plant genomes

Plant genomes provide essential and vital basic resources for studying many aspects of plant biology and applications (for example, breeding). From 2000 to 2020, 1,144 genomes of 782 plant species were sequenced. In the past three years (2021-2023), 2,373 genomes of 1,031 plant species, including 793 newly sequenced species, have been assembled, representing a great leap. The 2,373 newly assembled genomes, of which 63 are telomere-to-telomere assemblies and 921 have been generated in pan-genome projects, cover the major phylogenetic clades. Substantial advances in read length, throughput, accuracy and cost-effectiveness have notably simplified the achievement of high-quality assemblies. Moreover, the development of multiple software tools using different algorithms offers the opportunity to generate more complete and complex assemblies. A database named N3: plants, genomes, technologies has been developed to accommodate the metadata associated with the 3,517 genomes that have been sequenced from 1,575 plant species since 2000. We also provide an outlook for emerging opportunities in plant genome sequencing.

Gibberellic acid promotes single-celled fiber elongation through the activation of two signaling cascades in cotton

The agricultural green revolution spectacularly enhanced crop yield through modification of gibberellin (GA) signaling. However, in cotton, the GA signaling cascades remain elusive, limiting our potential to cultivate new cotton varieties and improve yield and quality. Here, we identified that GA prominently stimulated fiber elongation through the degradation of DELLA protein GhSLR1, thereby disabling GhSLR1's physical interaction with two transcription factors, GhZFP8 and GhBLH1. Subsequently, the resultant free GhBLH1 binds to GhKCS12 promoter and activates its expression to enhance VLCFAs biosynthesis. With a similar mechanism, the free GhZFP8 binds to GhSDCP1 promoter and activates its expression. As a result, GhSDCP1 upregulates the expression of GhPIF3 gene associated with plant cell elongation. Ultimately, the two parallel signaling cascades synergistically promote cotton fiber elongation. Our findings outline the mechanistic framework that translates the GA signal into fiber cell elongation, thereby offering a roadmap to improve cotton fiber quality and yield.

EARLY FLOWERING is a dominant gain-of-function allele of FANTASTIC FOUR 1/2c that promotes early flowering in tomato

Flowering time, an important factor in plant adaptability and genetic improvement, is regulated by various genes in tomato (Solanum lycopersicum). In this study, we characterized a tomato mutant, EARLY FLOWERING (EF), that developed flowers much earlier than its parental control. EF is a dominant gain-of-function allele with a T-DNA inserted 139 bp downstream of the stop codon of FANTASTIC FOUR 1/2c (FAF1/2c). The transcript of SlFAF1/2c was at elevated levels in the EF mutant. Overexpressing SlFAF1/2c in tomato plants phenocopied the early flowering trait of the EF mutant. Knocking out SlFAF1/2c in the EF mutant reverted the early flowering phenotype of the mutant to the normal flowering time of the wild-type tomato plants. SlFAF1/2c promoted the floral transition by shortening the vegetative phase rather than by reducing the number of leaves produced before the emergence of the first inflorescence. The COP9 signalosome subunit 5B (CSN5B) was shown to interact with FAF1/2c, and knocking out CSN5B led to an early flowering phenotype in tomato. Interestingly, FAF1/2c was found to reduce the accumulation of the CSN5B protein by reducing its protein stability. These findings imply that FAF1/2c regulates flowering time in tomato by reducing the accumulation and stability of CSN5B, which influences the expression of SINGLE FLOWER TRUSS (SFT), JOINTLESS (J) and UNIFLORA (UF). Thus, a new allele of SlFAF1/2c was discovered and found to regulate flowering time in tomato.

Arabidopsis as a model for translational research

Arabidopsis thaliana is currently the most-studied plant species on earth, with an unprecedented number of genetic, genomic, and molecular resources having been generated in this plant model. In the era of translating foundational discoveries to crops and beyond, we aimed to highlight the utility and challenges of using Arabidopsis as a reference for applied plant biology research, agricultural innovation, biotechnology, and medicine. We hope that this review will inspire the next generation of plant biologists to continue leveraging Arabidopsis as a robust and convenient experimental system to address fundamental and applied questions in biology. We aim to encourage lab and field scientists alike to take advantage of the vast Arabidopsis datasets, annotations, germplasm, constructs, methods, molecular and computational tools in our pursuit to advance understanding of plant biology and help feed the world's growing population. We envision that the power of Arabidopsis-inspired biotechnologies and foundational discoveries will continue to fuel the development of resilient, high-yielding, nutritious plants for the betterment of plant and animal health and greater environmental sustainability.

Precise fine-turning of GhTFL1 by base editing tools defines ideal cotton plant architecture

BACKGROUND

CRISPR/Cas-derived base editor enables precise editing of target sites and has been widely used for basic research and crop genetic improvement. However, the editing efficiency of base editors at different targets varies greatly.

RESULTS

Here, we develop a set of highly efficient base editors in cotton plants. GhABE8e, which is fused to conventional nCas9, exhibits 99.9% editing efficiency, compared to GhABE7.10 with 64.9%, and no off-target editing is detected. We further replace nCas9 with dCpf1, which recognizes TTTV PAM sequences, to broaden the range of the target site. To explore the functional divergence of TERMINAL FLOWER 1 (TFL1), we edit the non-coding and coding regions of GhTFL1 with 26 targets to generate a comprehensive allelic population including 300 independent lines in cotton. This allows hidden pleiotropic roles for GhTFL1 to be revealed and allows us to rapidly achieve directed domestication of cotton and create ideotype germplasm with moderate height, shortened fruiting branches, compact plant, and early-flowering. Further, by exploring the molecular mechanism of the GhTFL1L86P and GhTFL1K53G+S78G mutations, we find that the GhTFL1L86P mutation weakens the binding strength of the GhTFL1 to other proteins but does not lead to a complete loss of GhTFL1 function.

CONCLUSIONS

This strategy provides an important technical platform and genetic information for the study and creation of ideal plant architecture.

A comprehensive review on Gossypium hirsutum resistance against cotton leaf curl virus

Cotton (Gossypium hirsutum L.) is a significant fiber crop. Being a major contributor to the textile industry requires continuous care and attention. Cotton is subjected to various biotic and abiotic constraints. Among these, biotic factors including cotton leaf curl virus (CLCuV) are dominant. CLCuV is a notorious disease of cotton and is acquired, carried, and transmitted by the whitefly (Bemisia tabaci). A cotton plant affected with CLCuV may show a wide range of symptoms such as yellowing of leaves, thickening of veins, upward or downward curling, formation of enations, and stunted growth. Though there are many efforts to protect the crop from CLCuV, long-term results are not yet obtained as CLCuV strains are capable of mutating and overcoming plant resistance. However, systemic-induced resistance using a gene-based approach remained effective until new virulent strains of CLCuV (like Cotton Leaf Curl Burewala Virus and others) came into existence. Disease control by biological means and the development of CLCuV-resistant cotton varieties are in progress. In this review, we first discussed in detail the evolution of cotton and CLCuV strains, the transmission mechanism of CLCuV, the genetic architecture of CLCuV vectors, and the use of pathogen and nonpathogen-based approaches to control CLCuD. Next, we delineate the uses of cutting-edge technologies like genome editing (with a special focus on CRISPR-Cas), next-generation technologies, and their application in cotton genomics and speed breeding to develop CLCuD resistant cotton germplasm in a short time. Finally, we delve into the current obstacles related to cotton genome editing and explore forthcoming pathways for enhancing precision in genome editing through the utilization of advanced genome editing technologies. These endeavors aim to enhance cotton's resilience against CLCuD.

Dynamic Phytomeric Growth Contributes to Local Adaptation in Barley

Vascular plants have segmented body axes with iterative nodes and internodes. Appropriate node initiation and internode elongation are fundamental to plant fitness and crop yield; however, how these events are spatiotemporally coordinated remains elusive. We show that in barley (Hordeum vulgare L.), selections during domestication have extended the apical meristematic phase to promote node initiation, but constrained subsequent internode elongation. In both vegetative and reproductive phases, internode elongation displays a dynamic proximal-distal gradient, and among subpopulations of domesticated barleys worldwide, node initiation and proximal internode elongation are associated with latitudinal and longitudinal gradients, respectively. Genetic and functional analyses suggest that, in addition to their converging roles in node initiation, flowering-time genes have been repurposed to specify the timing and duration of internode elongation. Our study provides an integrated view of barley node initiation and internode elongation and suggests that plant architecture should be recognized as a collection of dynamic phytomeric units in the context of crop adaptive evolution.

Arabidopsis and Maize Terminator Strength is Determined by GC Content, Polyadenylation Motifs and Cleavage Probability

The 3' end of a gene, often called a terminator, modulates mRNA stability, localization, translation, and polyadenylation. Here, we adapted Plant STARR-seq, a massively parallel reporter assay, to measure the activity of over 50,000 terminators from the plants Arabidopsis thaliana and Zea mays. We characterize thousands of plant terminators, including many that outperform bacterial terminators commonly used in plants. Terminator activity is species-specific, differing in tobacco leaf and maize protoplast assays. While recapitulating known biology, our results reveal the relative contributions of polyadenylation motifs to terminator strength. We built a computational model to predict terminator strength and used it to conduct in silico evolution that generated optimized synthetic terminators. Additionally, we discover alternative polyadenylation sites across tens of thousands of terminators; however, the strongest terminators tend to have a dominant cleavage site. Our results establish features of plant terminator function and identify strong naturally occurring and synthetic terminators.

GRASSY TILLERS1 (GT1) and SIX-ROWED SPIKE1 (VRS1) homologs share conserved roles in growth repression

Crop engineering and de novo domestication using gene editing are new frontiers in agriculture. However, outside of well-studied crops and model systems, prioritizing engineering targets remains challenging. Evolution can guide us, revealing genes with deeply conserved roles that have repeatedly been selected in the evolution of plant form. Homologs of the transcription factor genes GRASSY TILLERS1 (GT1) and SIX-ROWED SPIKE1 (VRS1) have repeatedly been targets of selection in domestication and evolution, where they repress growth in many developmental contexts. This suggests a conserved role for these genes in regulating growth repression. To test this, we determined the roles of GT1 and VRS1 homologs in maize (Zea mays) and the distantly related grass brachypodium (Brachypodium distachyon) using gene editing and mutant analysis. In maize, gt1; vrs1-like1 (vrl1) mutants have derepressed growth of floral organs. In addition, gt1; vrl1 mutants bore more ears and more branches, indicating broad roles in growth repression. In brachypodium, Bdgt1; Bdvrl1 mutants have more branches, spikelets, and flowers than wild-type plants, indicating conserved roles for GT1 and VRS1 homologs in growth suppression over ca. 59 My of grass evolution. Importantly, many of these traits influence crop productivity. Notably, maize GT1 can suppress growth in arabidopsis (Arabidopsis thaliana) floral organs, despite ca. 160 My of evolution separating the grasses and arabidopsis. Thus, GT1 and VRS1 maintain their potency as growth regulators across vast timescales and in distinct developmental contexts. This work highlights the power of evolution to inform gene editing in crop improvement.

Design principles for synthetic control systems to engineer plants

KEY MESSAGE

Synthetic control systems have led to significant advancement in the study and engineering of unicellular organisms, but it has been challenging to apply these tools to multicellular organisms like plants. The ability to predictably engineer plants will enable the development of novel traits capable of alleviating global problems, such as climate change and food insecurity. Engineering predictable multicellular phenotypes will require the development of synthetic control systems that can precisely regulate how the information encoded in genomes is translated into phenotypes. Many efficient control systems have been developed for unicellular organisms. However, it remains challenging to use such tools to study or engineer multicellular organisms. Plants are a good chassis within which to develop strategies to overcome these challenges, thanks to their capacity to withstand large-scale reprogramming without lethality. Additionally, engineered plants have great potential for solving major societal problems. Here we briefly review the progress of control system development in unicellular organisms, and how that information can be leveraged to characterize control systems in plants. Further, we discuss strategies for developing control systems designed to regulate the expression of transgenes or endogenous loci and generate dosage-dependent or discrete traits. Finally, we discuss the utility that mathematical models of biological processes have for control system deployment.

Parallel tuning of semi-dwarfism via differential splicing of Brachytic1 in commercial maize and smallholder sorghum

In the current genomic era, the search and deployment of new semi-dwarf alleles have continued to develop better plant types in all cereals. We characterized an agronomically optimal semi-dwarf mutation in Zea mays L. and a parallel polymorphism in Sorghum bicolor L. We cloned the maize brachytic1 (br1-Mu) allele by a modified PCR-based Sequence Amplified Insertion Flanking Fragment (SAIFF) approach. Histology and RNA-Seq elucidated the mechanism of semi-dwarfism. GWAS linked a sorghum plant height QTL with the Br1 homolog by resequencing a West African sorghum landraces panel. The semi-dwarf br1-Mu allele encodes an MYB transcription factor78 that positively regulates stalk cell elongation by interacting with the polar auxin pathway. Semi-dwarfism is due to differential splicing and low functional Br1 wild-type transcript expression. The sorghum ortholog, SbBr1, co-segregates with the major plant height QTL qHT7.1 and is alternatively spliced. The high frequency of the Sbbr1 allele in African landraces suggests that African smallholder farmers used the semi-dwarf allele to improve plant height in sorghum long before efforts to introduce Green Revolution-style varieties in the 1960s. Surprisingly, variants for differential splicing of Brachytic1 were found in both commercial maize and smallholder sorghum, suggesting parallel tuning of plant architecture across these systems.

CRISPR/Cas as a Genome-Editing Technique in Fruit Tree Breeding

CRISPR (short for "Clustered Regularly Interspaced Short Palindromic Repeats") is a technology that research scientists use to selectively modify the DNA of living organisms. CRISPR was adapted for use in the laboratory from the naturally occurring genome-editing systems found in bacteria. In this work, we reviewed the methods used to introduce CRISPR/Cas-mediated genome editing into fruit species, as well as the impacts of the application of this technology to activate and knock out target genes in different fruit tree species, including on tree development, yield, fruit quality, and tolerance to biotic and abiotic stresses. The application of this gene-editing technology could allow the development of new generations of fruit crops with improved traits by targeting different genetic segments or even could facilitate the introduction of traits into elite cultivars without changing other traits. However, currently, the scarcity of efficient regeneration and transformation protocols in some species, the fact that many of those procedures are genotype-dependent, and the convenience of segregating the transgenic parts of the CRISPR system represent the main handicaps limiting the potential of genetic editing techniques for fruit trees. Finally, the latest news on the legislation and regulations about the use of plants modified using CRISPR/Cas systems has been also discussed.

TaACTIN7-D regulates plant height and grain shape in bread wheat

Exploitation of new gene resources and genetic networks contributing to the control of crop yield-related traits, such as plant height, grain size, and shape, may enable us to breed modern high-yielding wheat varieties through molecular methods. In this study, via ethylmethanesulfonate mutagenesis, we identify a wheat mutant plant, mu-597, that shows semi-dwarf plant architecture and round grain shape. Through bulked segregant RNA-seq and map-based cloning, the causal gene for the semi-dwarf phenotype of mu-597 is located. We find that a single-base mutation in the coding region of TaACTIN7-D (TaACT7-D), leading to a Gly-to-Ser (G65S) amino acid mutation at the 65th residue of the deduced TaACT7-D protein, can explain the semi-dwarfism and round grain shape of mu-597. Further evidence shows that the G65S mutation in TaACT7-D hinders the polymerization of actin from monomeric (G-actin) to filamentous (F-actin) status while attenuates wheat responses to multiple phytohormones, including brassinosteroids, auxin, and gibberellin. Together, these findings not only define a new semi-dwarfing gene resource that can be potentially used to design plant height and grain shape of bread wheat but also establish a direct link between actin structure modulation and phytohormone signal transduction.

Genome evolution and initial breeding of the Triticeae grass Leymus chinensis dominating the Eurasian Steppe

Leymus chinensis, a dominant perennial grass in the Eurasian Steppe, is well known for its remarkable adaptability and forage quality. Hardly any breeding has been done on the grass, limiting its potential in ecological restoration and forage productivity. To enable genetic improvement of the untapped, important species, we obtained a 7.85-Gb high-quality genome of L. chinensis with a particularly long contig N50 (318.49 Mb). Its allotetraploid genome is estimated to originate 5.29 million years ago (MYA) from a cross between the Ns-subgenome relating to Psathyrostachys and the unknown Xm-subgenome. Multiple bursts of transposons during 0.433-1.842 MYA after genome allopolyploidization, which involved predominantly the Tekay and Angela of LTR retrotransposons, contributed to its genome expansion and complexity. With the genome resource available, we successfully developed a genetic transformation system as well as the gene-editing pipeline in L. chinensis. We knocked out the monocot-specific miR528 using CRISPR/Cas9, resulting in the improvement of yield-related traits with increases in the tiller number and growth rate. Our research provides valuable genomic resources for Triticeae evolutionary studies and presents a conceptual framework illustrating the utilization of genomic information and genome editing to accelerate the improvement of wild L. chinensis with features such as polyploidization and self-incompatibility.

Current status, breeding strategies and future prospects for managing chilli leaf curl virus disease and associated begomoviruses in Chilli (Capsicum spp.)

Chilli leaf curl virus disease caused by begomoviruses, has emerged as a major threat to global chilli production, causing severe yield losses and economic harm. Begomoviruses are a highly successful and emerging group of plant viruses that are primarily transmitted by whiteflies belonging to the Bemisia tabaci complex. The most effective method for mitigating chilli leaf curl virus disease losses is breeding for host resistance to Begomovirus. This review highlights the current situation of chilli leaf curl virus disease and associated begomoviruses in chilli production, stressing the significant issues that breeders and growers confront. In addition, the various breeding methods used to generate begomovirus resistant chilli cultivars, and also the complicated connections between the host plant, vector and the virus are discussed. This review highlights the importance of resistance breeding, emphasising the importance of multidisciplinary approaches that combine the best of traditional breeding with cutting-edge genomic technologies. subsequently, the article highlights the challenges that must be overcome in order to effectively deploy begomovirus resistant chilli varieties across diverse agroecological zones and farming systems, as well as understanding the pathogen thus providing the opportunities for improving the sustainability and profitability of chilli production.

Phytohormone biosynthesis and transcriptional analyses provide insight into the main growth stage of male and female cones Pinus koraiensis

The cone is a crucial component of the whole life cycle of gymnosperm and an organ for sexual reproduction of gymnosperms. In Pinus koraiensis, the quantity and development process of male and female cones directly influence seed production, which in turn influences the tree's economic value. There are, however, due to the lack of genetic information and genomic data, the morphological development and molecular mechanism of female and male cones of P. koraiensis have not been analyzed. Long-term phenological observations were used in this study to document the main process of the growth of both male and female cones. Transcriptome sequencing and endogenous hormone levels at three critical developmental stages were then analyzed to identify the regulatory networks that control these stages of cones development. The most significant plant hormones influencing male and female cones growth were discovered to be gibberellin and brassinosteroids, according to measurements of endogenous hormone content. Additionally, transcriptome sequencing allowed the identification of 71,097 and 31,195 DEGs in male and female cones. The synthesis and control of plant hormones during cones growth were discovered via enrichment analysis of key enrichment pathways. FT and other flowering-related genes were discovered in the coexpression network of flower growth development, which contributed to the growth development of male and female cones of P. koraiensis. The findings of this work offer a cutting-edge foundation for understanding reproductive biology and the molecular mechanisms that control the growth development of male and female cones in P. koraiensis.

Grain yield improvement by genome editing of TaARF12 that decoupled peduncle and rachis development trajectories via differential regulation of gibberellin signalling in wheat

Plant breeding is constrained by trade-offs among different agronomic traits by the pleiotropic nature of many genes. Genes that contribute to two or more favourable traits with no penalty on yield are rarely reported, especially in wheat. Here, we describe the editing of a wheat auxin response factor TaARF12 by using CRISPR/Cas9 that rendered shorter plant height with larger spikes. Changes in plant architecture enhanced grain number per spike up to 14.7% with significantly higher thousand-grain weight and up to 11.1% of yield increase under field trials. Weighted Gene Co-Expression Network Analysis (WGCNA) of spatial-temporal transcriptome profiles revealed two hub genes: RhtL1, a DELLA domain-free Rht-1 paralog, which was up-regulated in peduncle, and TaNGR5, an organ size regulator that was up-regulated in rachis, in taarf12 plants. The up-regulation of RhtL1 in peduncle suggested the repression of GA signalling, whereas up-regulation of TaNGR5 in spike may promote GA response, a working model supported by differential expression patterns of GA biogenesis genes in the two tissues. Thus, TaARF12 complemented plant height reduction with larger spikes that gave higher grain yield. Manipulation of TaARF12 may represent a new strategy in trait pyramiding for yield improvement in wheat.

Plant fructans: Recent advances in metabolism, evolution aspects and applications for human health

Fructans, fructose polymers, are one of the three major reserve carbohydrate in plants. The nutritional and therapeutic benefits of natural fructans in plants have attracted increasing interest by consumers and food industry. In the course of evolution, many plants have developed the ability of regulating plant fructans metabolism to produce fructans with different structures and chain lengths, which are strongly correlated with their survival in harsh environments. Exploring these evolution-related genes in fructans biosynthesis and de novo domestication of fructans-rich plants based on genome editing is a viable and promising approach to improve human dietary quality and reduce the risk of chronic disease. These advances will greatly facilitate breeding and production of tailor-made fructans as a healthy food ingredient from wild plants such as huangjing (Polygonatum cyrtonema). The purpose of this review is to broaden our knowledge on plant fructans biosynthesis, evolution and benefits to human health.

The master growth regulator DELLA binding to histone H2A is essential for DELLA-mediated global transcription regulation

The DELLA genes, also known as 'Green Revolution' genes, encode conserved master growth regulators that control plant development in response to internal and environmental cues. Functioning as nuclear-localized transcription regulators, DELLAs modulate expression of target genes via direct protein-protein interaction of their carboxy-terminal GRAS domain with hundreds of transcription factors (TFs) and epigenetic regulators. However, the molecular mechanism of DELLA-mediated transcription reprogramming remains unclear. Here by characterizing new missense alleles of an Arabidopsis DELLA, repressor of ga1-3 (RGA), and co-immunoprecipitation assays, we show that RGA binds histone H2A via the PFYRE subdomain within its GRAS domain to form a TF-RGA-H2A complex at the target chromatin. Chromatin immunoprecipitation followed by sequencing analysis further shows that this activity is essential for RGA association with its target chromatin globally. Our results indicate that, although DELLAs are recruited to target promoters by binding to TFs via the LHR1 subdomain, DELLA-H2A interaction via the PFYRE subdomain is necessary to stabilize the TF-DELLA-H2A complex at the target chromatin. This study provides insights into the two distinct key modular functions in DELLA for its genome-wide transcription regulation in plants.

Modulating auxin response stabilizes tomato fruit set

Fruit formation depends on successful fertilization and is highly sensitive to weather fluctuations that affect pollination. Auxin promotes fruit initiation and growth following fertilization. Class A auxin response factors (Class A ARFs) repress transcription in the absence of auxin and activate transcription in its presence. Here, we explore how multiple members of the ARF family regulate fruit set and fruit growth in tomato (Solanum lycopersicum) and Arabidopsis thaliana, and test whether reduction of SlARF activity improves yield stability in fluctuating temperatures. We found that several tomato Slarf mutant combinations produced seedless parthenocarpic fruits, most notably mutants deficient in SlARF8A and SlARF8B genes. Arabidopsis Atarf8 mutants deficient in the orthologous gene had less complete parthenocarpy than did tomato Slarf8a Slarf8b mutants. Conversely, Atarf6 Atarf8 double mutants had reduced fruit growth after fertilization. AtARF6 and AtARF8 likely switch from repression to activation of fruit growth in response to a fertilization-induced auxin increase in gynoecia. Tomato plants with reduced SlARF8A and SlARF8B gene dosage had substantially higher yield than the wild type under controlled or ambient hot and cold growth conditions. In field trials, partial reduction in the SlARF8 dose increased yield under extreme temperature with minimal pleiotropic effects. The stable yield of the mutant plants resulted from a combination of early onset of fruit set, more fruit-bearing branches and more flowers setting fruits. Thus, ARF8 proteins mediate the control of fruit set, and relieving this control with Slarf8 mutations may be utilized in breeding to increase yield stability in tomato and other crops.

CRISPR/Cas9 mutants delineate roles of Populus FT and TFL1/CEN/BFT family members in growth, dormancy release and flowering

Vegetative and reproductive phase change and phenology are economically and ecologically important traits. Trees typically require several years of growth before flowering and, once mature, seasonal control of the transition to flowering and flower development is necessary to maintain vegetative meristems and for reproductive success. Members of two related gene subfamilies, FLOWERING LOCUST (FT) and TERMINAL FLOWER1 (TFL1)/CENTRORADIALIS (CEN)/BROTHER OF FT AND TFL1 (BFT), have antagonistic roles in flowering in diverse species and roles in vegetative phenology in trees, but many details of their functions in trees have yet to be resolved. Here, we used CRISPR/Cas9 to generate single and double mutants involving the five Populus FT and TFL1/CEN/BFT genes. The ft1 mutants exhibited wild-type-like phenotypes in long days and short days, but after chilling, to release dormancy, they showed delayed bud flush and GA3 could compensate for the ft1 mutation. After rooting and generating some phytomers in tissue culture, both cen1 and cen1ft1 mutants produced terminal as well as axillary flowers, indicating that the cen1 flowering phenotype is independent of FT1. The CEN1 showed distinct circannual expression patterns in vegetative and reproductive tissues and comparison with the expression patterns of FT1 and FT2 suggests that the relative levels of CEN1 compared with FT1 and FT2 regulate multiple phases of vegetative and reproductive seasonal development.

Diversity of woodland strawberry inflorescences arises from heterochrony regulated by TERMINAL FLOWER 1 and FLOWERING LOCUS T

A vast variety of inflorescence architectures have evolved in angiosperms. Here, we analyze the diversity and development of the woodland strawberry (Fragaria vesca) inflorescence. Contrary to historical classifications, we show that it is a closed thyrse: a compound inflorescence with determinate primary monopodial axis and lateral sympodial branches, thus combining features of racemes and cymes. We demonstrate that this architecture is generated by 2 types of inflorescence meristems differing in their geometry. We further show that woodland strawberry homologs of TERMINAL FLOWER 1 (FvTFL1) and FLOWERING LOCUS T (FvFT1) regulate the development of both the racemose and cymose components of the thyrse. Loss of functional FvTFL1 reduces the number of lateral branches of the main axis and iterations in the lateral branches but does not affect their cymose pattern. These changes can be enhanced or compensated by altering FvFT1 expression. We complement our experimental findings with a computational model that captures inflorescence development using a small set of rules. The model highlights the distinct regulation of the fate of the primary and higher-order meristems, and explains the phenotypic diversity among inflorescences in terms of heterochrony resulting from the opposite action of FvTFL1 and FvFT1 within the thyrse framework. Our results represent a detailed analysis of thyrse architecture development at the meristematic and molecular levels.

The GATA transcription factor TaGATA1 recruits demethylase TaELF6-A1 and enhances seed dormancy in wheat by directly regulating TaABI5

Seed dormancy is an important agronomic trait in crops, and plants with low dormancy are prone to preharvest sprouting (PHS) under high-temperature and humid conditions. In this study, we report that the GATA transcription factor TaGATA1 is a positive regulator of seed dormancy by regulating TaABI5 expression in wheat. Our results demonstrate that TaGATA1 overexpression significantly enhances seed dormancy and increases resistance to PHS in wheat. Gene expression patterns, abscisic acid (ABA) response assay, and transcriptome analysis all indicate that TaGATA1 functions through the ABA signaling pathway. The transcript abundance of TaABI5, an essential regulator in the ABA signaling pathway, is significantly elevated in plants overexpressing TaGATA1. Chromatin immunoprecipitation assay (ChIP) and transient expression analysis showed that TaGATA1 binds to the GATA motifs at the promoter of TaABI5 and induces its expression. We also demonstrate that TaGATA1 physically interacts with the putative demethylase TaELF6-A1, the wheat orthologue of Arabidopsis ELF6. ChIP-qPCR analysis showed that H3K27me3 levels significantly decline at the TaABI5 promoter in the TaGATA1-overexpression wheat line and that transient expression of TaELF6-A1 reduces methylation levels at the TaABI5 promoter, increasing TaABI5 expression. These findings reveal a new transcription module, including TaGATA1-TaELF6-A1-TaABI5, which contributes to seed dormancy through the ABA signaling pathway and epigenetic reprogramming at the target site. TaGATA1 could be a candidate gene for improving PHS resistance.

Prospects for rice in 2050

A key to achieve the goals put forward in the UN's 2030 Agenda for Sustainable Development, it will need transformative change to our agrifood systems. We must mount to the global challenge to achieve food security in a sustainable manner in the context of climate change, population growth, urbanization, and depletion of natural resources. Rice is one of the major staple cereal crops that has contributed, is contributing, and will still contribute to the global food security. To date, rice yield has held pace with increasing demands, due to advances in both fundamental and biological studies, as well as genomic and molecular breeding practices. However, future rice production depends largely on the planting of resilient cultivars that can acclimate and adapt to changing environmental conditions. This Special Issue highlight with reviews and original research articles the exciting and growing field of rice-environment interactions that could benefit future rice breeding. We also outline open questions and propose future directions of 2050 rice research, calling for more attentions to develop environment-resilient rice especially hybrid rice, upland rice and perennial rice.

New semi-dwarfing alleles with increased coleoptile length by gene editing of gibberellin 3-oxidase 1 using CRISPR-Cas9 in barley (Hordeum vulgare L.)

The green revolution was based on genetic modification of the gibberellin (GA) hormone system with "dwarfing" gene mutations that reduces GA signals, conferring shorter stature, thus enabling plant adaptation to modern farming conditions. Strong GA-related mutants with shorter stature often have reduced coleoptile length, discounting yield gain due to their unsatisfactory seedling emergence under drought conditions. Here we present gibberellin (GA) 3-oxidase1 (GA3ox1) as an alternative semi-dwarfing gene in barley that combines an optimal reduction in plant height without restricting coleoptile and seedling growth. Using large-scale field trials with an extensive collection of barley accessions, we showed that a natural GA3ox1 haplotype moderately reduced plant height by 5-10 cm. We used CRISPR/Cas9 technology, generated several novel GA3ox1 mutants and validated the function of GA3ox1. We showed that altered GA3ox1 activities changed the level of active GA isoforms and consequently increased coleoptile length by an average of 8.2 mm, which could provide essential adaptation to maintain yield under climate change. We revealed that CRISPR/Cas9-induced GA3ox1 mutations increased seed dormancy to an ideal level that could benefit the malting industry. We conclude that selecting HvGA3ox1 alleles offers a new opportunity for developing barley varieties with optimal stature, longer coleoptile and additional agronomic traits.

An efficient CRISPR-Cas12a promoter editing system for crop improvement

Promoter editing represents an innovative approach to introduce quantitative trait variation (QTV) in crops. However, an efficient promoter editing system for QTV needs to be established. Here we develop a CRISPR-Cas12a promoter editing (CAPE) system that combines a promoter key-region estimating model and an efficient CRISPR-Cas12a-based multiplexed or singular editing system. CAPE is benchmarked in rice to produce QTV continuums for grain starch content and size by targeting OsGBSS1 and OsGS3, respectively. We then apply CAPE for promoter editing of OsD18, a gene encoding GA3ox in the gibberellin biosynthesis pathway. The resulting lines carry a QTV continuum of semidwarfism without significantly compromising grain measures. Field trials demonstrated that the OsD18 promoter editing lines have the same yield performance and antilodging phenotype as the Green Revolution OsSD1 mutants in different genetic backgrounds. Hence, promoter editing of OsD18 generates a quantitative Green Revolution trait. Together, we demonstrate a CAPE-based promoter editing and tuning pipeline for efficient production of useful QTV continuum in crops.

MdbZIP74 negatively regulates osmotic tolerance and adaptability to moderate drought conditions of apple plants

Drought is the most prominent threat to global agricultural production. The basic leucine zipper (bZIP) family is related to the response to a series of abiotic stress. In this case, apple calli and the seedlings of MdbZIP74-RNAi transgenic lines were obtained. Under osmotic stress and moderate drought conditions, the content of malondialdehyde, relative water content and other stress-related assays were measured. MdbZIP74 was found to negatively regulate the osmotic tolerance of apple callus. The growth of MdbZIP74-RNAi calli enhanced resistance without significant production loss. The silencing of MdbZIP74 contributes to redox balance and the adaptability of apple seedlings to moderate drought conditions. Four related differentially expressed genes in the biosynthesis of cytokinin and catabolic pathway were identified through a transcriptome analysis of MdbZIP74-RNAi seedlings under moderate drought conditions. MdLOG8 was further identified as the target of MdbZIP74 involved in the drought adaptability of apple plants using a dual experiment. Further confirmation showed MdLOG8 was maintained in the MdbZIP74-RNAi seedlings presumably acting as the growth regulator to enhance drought adaptability. It was concluded that the correct regulation of cytokinin level under moderate drought conditions maintains the redox balance and avoids the situation of plants surviving with the minimal resources.

Discontinuous low temperature stress and plant growth regulators during the germination period promote roots growth in alfalfa (Medicago sativa L.)

In high-cold regions, alfalfa is susceptible to cold damage during the seed germination. The effects of discontinuous low temperature stress and plant growth regulators (PGRs) on alfalfa were studied in response to the high day/night temperature differentials in the area. The experiments included seed germination, seedling cold tolerance and plant recovery. Variable temperatures (VT) of 0 °C/15 °C, 5 °C/20 °C and 10 °C/25 °C were set and seeds were soaked with alginate oligosaccharides (AOS), brassinolide (BR) and diethyl aminoethyl hexanoate (DA-6) during the germination period. Parameters such as seed germination and mean germination time (MGT), phenylalanine ammonia-lyase (PAL) activity and oligomeric proanthocyanidins (OPC) content of early seedlings, dry matter accumulation and root crown of the restored plants were analysed. The results showed that low variable-temperature (LVT) stress prolonged the MGT but had little inhibitory effect on germination percentage. Early seedlings adapted to LVT stress by regulating their own water and OPC content, PAL activity and other parameters. LVT induced early alfalfa seedlings to increase their underground biomass by shortening root length and increasing root diameter, and those that had accumulated more underground biomass had faster growth rates and higher total biomass when the ambient temperature rose. AOS also promoted an increase in root crown diameter and root dry weight. This research proved that LVT stress and AOS during the germination process can lead to better growth of alfalfa in high cold regions.

CRISPR/Cas9-mediated editing of Wx and BADH2 genes created glutinous and aromatic two-line hybrid rice

Amylose content (AC) is one of the physicochemical indexes of rice quality, which is largely determined by the Waxy (Wx) gene. Fragrance in rice is favored because it adds good flavor and a faint scent. Loss of function of the BADH2 (FGR) gene promotes the biosynthesis of 2-acetyl-1-pyrroline (2AP), which is the main compound responsible for aroma in rice. Here, we used a CRISPR/Cas9 system to simultaneously knock out Wx and FGR genes in 1892S and M858, which are the parents of an indica two-line hybrid rice, Huiliangyou 858 (HLY858). Four T-DNA-free homozygous mutants (1892Swxfgr-1, 1892Swxfgr-2, M858wxfgr-1, and M858wxfgr-2) were obtained. The 1892Swxfgr and M858wxfgr were crossed to generate double mutant hybrid lines HLY858wxfgr-1 and HLY858wxfgr-2. Size-exclusion chromatography (SEC) data indicated that true AC of the wx mutant starches ranged from 0.22 to 1.63%, much lower than those of the wild types (12.93 to 13.76%). However, the gelatinization temperature (GT) of the wx mutants in backgrounds of 1892S, M858, and HLY858 were still high, and showed no significant differences with the wild type controls. The aroma compounds 2AP content in grains of HLY858wxfgr-1 and HLY858wxfgr-2 were 153.0 μg/kg and 151.0 μg/kg, respectively. In contrast, 2AP was not detected in grains of HLY858. There were no significant differences in major agronomic traits between the mutants and HLY858. This study provides guidelines for cultivation of ideal glutinous and aromatic hybrid rice by gene editing.

Spatio-temporal analysis of strawberry architecture: insights into the control of branching and inflorescence complexity

Plant architecture plays a major role in flowering and therefore in crop yield. Attempts to visualize and analyse strawberry plant architecture have been few to date. Here, we developed open-source software combining two- and three-dimensional representations of plant development over time along with statistical methods to explore the variability in spatio-temporal development of plant architecture in cultivated strawberry. We applied this software to six seasonal strawberry varieties whose plants were exhaustively described monthly at the node scale. Results showed that the architectural pattern of the strawberry plant is characterized by a decrease of the module complexity between the zeroth-order module (primary crown) and higher-order modules (lateral branch crowns and extension crowns). Furthermore, for each variety, we could identify traits with a central role in determining yield, such as date of appearance and number of branches. By modeling the spatial organization of axillary meristem fate on the zeroth-order module using a hidden hybrid Markov/semi-Markov mathematical model, we further identified three zones with different probabilities of production of branch crowns, dormant buds, or stolons. This open-source software will be of value to the scientific community and breeders in studying the influence of environmental and genetic cues on strawberry architecture and yield.

Tailoring crops with superior product quality through genome editing: an update

In this review, using genome editing, the quality trait alterations in important crops have been discussed, along with the challenges encountered to maintain the crop products' quality. The delivery of economic produce with superior quality is as important as high yield since it dictates consumer's acceptance and end use. Improving product quality of various agricultural and horticultural crops is one of the important targets of plant breeders across the globe. Significant achievements have been made in various crops using conventional plant breeding approaches, albeit, at a slower rate. To keep pace with ever-changing consumer tastes and preferences and industry demands, such efforts must be supplemented with biotechnological tools. Fortunately, many of the quality attributes are resultant of well-understood biochemical pathways with characterized genes encoding enzymes at each step. Targeted mutagenesis and transgene transfer have been instrumental in bringing out desired qualitative changes in crops but have suffered from various pitfalls. Genome editing, a technique for methodical and site-specific modification of genes, has revolutionized trait manipulation. With the evolution of versatile and cost effective CRISPR/Cas9 system, genome editing has gained significant traction and is being applied in several crops. The availability of whole genome sequences with the advent of next generation sequencing (NGS) technologies further enhanced the precision of these techniques. CRISPR/Cas9 system has also been utilized for desirable modifications in quality attributes of various crops such as rice, wheat, maize, barley, potato, tomato, etc. The present review summarizes salient findings and achievements of application of genome editing for improving product quality in various crops coupled with pointers for future research endeavors.

Crop domestication disrupts intercropping benefits: A case study from barley-faba bean mixture under contrasting P inputs

How crop domestication mediates root functional traits and trait plasticity in response to neighboring plants is unclear, but it is important for selecting potential species to be grown together to facilitate P uptake. We grew two barley accessions representing a two-stage domestication process as a sole crop or mixed with faba bean under low and high P inputs. We analyzed six root functional traits associated with P acquisition and plant P uptake in five cropping treatments in two pot experiments. The spatial and temporal patterns of root acid phosphatase activity were characterized in situ with zymography at 7, 14, 21, and 28 days after sowing in a rhizobox. Under low P supply, wild barley had higher total root length (TRL), specific root length (SRL), and root branching intensity (RootBr) as well as higher activity of acid phosphatase (APase) in the rhizosphere, but lower root exudation of carboxylates and mycorrhizal colonization (MC), relative to domesticated barley. In response to neighboring faba bean, wild barley exhibited larger plasticity in all root morphological traits (TRL, SRL, and RootBr), while domesticated barley showed greater plasticity in root exudates of carboxylates and colonization by mycorrhiza. Wild barley with greater root morphology-related trait plasticity was a better match with faba bean than domesticated barley, indicated by higher P uptake benefits in wild barley/faba bean than domesticated barley/faba bean mixtures under low P supply. Our findings indicated that the domestication of barley disrupts the intercropping benefits with faba bean through the shifts of root morphological traits and their plasticity in barley. Such findings provide valuable information for barley genotype breeding and the selection of species combinations to enhance P uptake.

Recent advances and future perspectives in early-maturing cotton research

Cotton's fundamental requirements for long periods of growth and specific seasonal temperatures limit the global arable areas that can be utilized to cultivate cotton. This constraint can be alleviated by breeding for early-maturing varieties. By delaying the sowing dates without impacting the boll-opening time, early-maturing varieties not only mitigate the yield losses brought on by unfavorable weathers in early spring and late autumn but also help reducing the competition between cotton and other crops for arable land, thereby optimizing the cropping system. This review presents studies and breeding efforts for early-maturing cotton, which efficiently pyramid early maturity, high-quality, multiresistance traits, and suitable plant architecture by leveraging pleiotropic genes. Attempts are also made to summarize our current understanding of the molecular mechanisms underlying early maturation, which involves many pathways such as epigenetic, circadian clock, and hormone signaling pathways. Moreover, new avenues and effective measures are proposed for fine-scale breeding of early-maturing crops to ensure the healthy development of the agricultural industry.

Gradual daylength sensing coupled with optimum cropping modes enhances multi-latitude adaptation of rice and maize

To expand crop planting areas, reestablishment of crop latitude adaptation based on genetic variation in photoperiodic genes can be performed, but it is quite time consuming. By contrast, a crop variety that already exhibits multi-latitude adaptation has the potential to increase its planting areas to be more widely and quickly available. However, the importance and potential of multi-latitude adaptation of crop varieties have not been systematically described. Here, combining daylength-sensing data with the cropping system of elite rice and maize varieties, we found that varieties with gradual daylength sensing coupled with optimum cropping modes have an enhanced capacity for multi-latitude adaptation in China. Furthermore, this multi-latitude adaptation expanded their planting areas and indirectly improved China's nationwide rice and maize unit yield. Thus, coupling the daylength-sensing process with optimum cropping modes to enhance latitude adaptability of excellent varieties represents an exciting approach for deploying crop varieties with the potential to expand their planting areas and quickly improve nationwide crop unit yield in developing countries.

High-Throughput Base Editing-Mediated Artificial Evolution Streamlines Trait Gene Identification in Rice

Base Editing-Mediated Gene Evolution (BEMGE) method develops novel rice germplasms with mutations in any endogenous gene through employing both Cas9n-based cytosine and adenine base editors combined with an sgRNA library tiling the full-length coding region, for obtaining unknown functional SNPs. Here we describe the process of artificial evolution of OsALS1 in rice cells using BEMGE through Agrobacterium-mediated transformation. BEMGE method has the potential to generate numerous nucleotide changes to screen pivotal amino acids (AAs) and to accelerate crop improvement.

Application of CRISPR/Cas9-mediated gene editing for abiotic stress management in crop plants

Abiotic stresses, including drought, salinity, cold, heat, and heavy metals, extensively reducing global agricultural production. Traditional breeding approaches and transgenic technology have been widely used to mitigate the risks of these environmental stresses. The discovery of engineered nucleases as genetic scissors to carry out precise manipulation in crop stress-responsive genes and associated molecular network has paved the way for sustainable management of abiotic stress conditions. In this context, the clustered regularly interspaced short palindromic repeat-Cas (CRISPR/Cas)-based gene-editing tool has revolutionized due to its simplicity, accessibility, adaptability, flexibility, and wide applicability. This system has great potential to build up crop varieties with enhanced tolerance against abiotic stresses. In this review, we summarize the latest findings on understanding the mechanism of abiotic stress response in plants and the application of CRISPR/Cas-mediated gene-editing system towards enhanced tolerance to a multitude of stresses including drought, salinity, cold, heat, and heavy metals. We provide mechanistic insights on the CRISPR/Cas9-based genome editing technology. We also discuss applications of evolving genome editing techniques such as prime editing and base editing, mutant library production, transgene free and multiplexing to rapidly deliver modern crop cultivars adapted to abiotic stress conditions.

A Genomic Analysis of Bacillus megaterium HT517 Reveals the Genetic Basis of Its Abilities to Promote Growth and Control Disease in Greenhouse Tomato

Bacillus megaterium is well known as a plant growth-promoting rhizobacterium, but the relevant molecular mechanisms remain unclear. This study aimed to elucidate the effects of B. megaterium HT517 on the growth and development of and the control of disease in greenhouse tomato and its mechanism of action. A pot experiment was conducted to determine the effect of B. megaterium on tomato growth, and this experiment included the HT517 group (3.2 × 10⁸ cfu/pot) and the control group (inoculated with the same amount of sterilized suspension). An antagonistic experiment and a plate confrontation experiment were conducted to study the antagonistic effect of B. megaterium and Fusarium oxysporum f.sp. lycopersici. Liquid chromatography-mass spectrometry was used to determine the metabolite composition and metabolic pathway of HT517. PacBio+Illumina HiSeq sequencing was utilized for map sequencing of the samples. An in-depth analysis of the functional genes related to the secretion of these substances by functional bacteria was conducted. HT517 could secrete organic acids that solubilize phosphorus, promote root growth, secrete auxin, which that promotes early flowering and fruiting, and alkaloids, which control disease, and reduce the incidence of crown rot by 51.0%. The complete genome sequence indicated that the strain comprised one circular chromosome with a length of 5,510,339 bp (including four plasmids in the genome), and the GC content accounted for 37.95%. Seven genes (pyk, aceB, pyc, ackA, gltA, buk, and aroK) related to phosphate solubilization, five genes (trpA, trpB, trpS, TDO2, and idi) related to growth promotion, eight genes (hpaB, pheS, pheT, ileS, pepA, iucD, paaG, and kamA) related to disease control, and one gene cluster of synthetic surfactin were identified in this research. The identification of molecular biological mechanisms for extracellular secretion by the HT517 strain clarified that its organic acids solubilized phosphorus, that auxin promoted growth, and that alkaloids controlled tomato diseases.