The Role of Dwarfing Traits in Historical and Modern Agriculture with a Focus on Rice

OsMYB14, an R2R3-MYB transcription factor, regulates plant height through the control of hormone metabolism in rice

Plant growth must be regulated throughout the plant life cycle. The myeloblastosis (MYB) transcription factor (TF) family is one of the largest TF families and is involved in metabolism, lignin biosynthesis, and developmental processes. Here, we showed that OsMYB14, a rice R2R3-MYB TF, was expressed in leaves and roots, especially in rice culm and panicles, and that it localized to the nucleus. Overexpression of OsMYB14 (OsMYB14-ox) in rice resulted in a 30% reduction in plant height compared to that of the wild type (WT), while the height of the osmyb14-knockout (osmyb14-ko) mutant generated using the CRISPR/Cas9 system was not significantly different. Microscopic observations of the first internode revealed that the cell size did not differ significantly among the lines. RNA sequencing analysis revealed that genes associated with plant development, regulation, lipid metabolism, carbohydrate metabolism, and gibberellin (GA) and auxin metabolic processes were downregulated in the OsMYB14-ox line. Hormone quantitation revealed that inactive GA19 accumulated in OsMYB14-ox but not in the WT or knockout plants, suggesting that GA20 generation was repressed. Indole-3-acetic acid (IAA) and IAA-aspartate accumulated in OsMYB14-ox and osmyb14-ko, respectively. Indeed, real-time PCR analysis revealed that the expression of OsGA20ox1, encoding GA20 oxidase 1, and OsGH3-2, encoding IAA-amido synthetase, was downregulated in OsMYB14-ox and upregulated in osmyb14-ko. A protein-binding microarray revealed the presence of a consensus DNA-binding sequence, the ACCTACC-like motif, in the promoters of the OsGA20ox1 and GA20ox2 genes. These results suggest that OsMYB14 may act as a negative regulator of biological processes affecting plant height in rice by regulating GA biosynthesis and auxin metabolism.

Evolution of the sporophyte shoot axis and functions of TALE HD transcription factors in stem development

The stem is one of the major organs in seed plants and is important for plant survival as well as in agriculture. However, due to the lack of clear external landmarks in many species, its developmental and evolutionary processes are understudied compared to other organs. Recent approaches tackling these problems, especially those focused on KNOX1 and BLH transcription factors belonging to the TALE homeodomain superfamily have started unveiling the patterning process of nodes and internodes by connecting previously accumulated knowledge on lateral organ regulators. Fossil records played crucial roles in understanding the evolutionary process of the stem. The aim of this review is to introduce how the stem evolved from ancestorial sporophyte axes and to provide frameworks for future efforts in understanding the developmental process of this elusive but pivotal organ.

YABBY and diverged KNOX1 genes shape nodes and internodes in the stem

Plant stems comprise nodes and internodes that specialize in solute exchange and elongation. However, their boundaries are not well defined, and how these basic units arise remains elusive. In rice with clear nodes and internodes, we found that one subclade of class I knotted1-like homeobox (KNOX1) genes for shoot meristem indeterminacy restricts node differentiation and allows internode formation by repressing YABBY genes for leaf development and genes from another node-specific KNOX1 subclade. YABBYs promote nodal vascular differentiation and limit stem elongation. YABBY and node-specific KNOX1 genes specify the pulvinus, which further elaborates the nodal structure for gravitropism. Notably, this KNOX1 subclade organization is specific to seed plants. We propose that nodes and internodes are distinct domains specified by YABBY-KNOX1 cross-regulation that diverged in early seed plants.

Identification and characterization of CsERECTA, a major gene controlling stem elongation through regulating GA biosynthesis in cucumber

Dwarfing is an ideal agronomic trait in crop breeding, which can improve lodging resistance and increase crop productivity. In this study, we identified a dwarf mutant cp-3 from an EMS-mutagenized population, which had extremely short internodes, and the cell length and number of internodes were significantly reduced. Meanwhile, exogenous GA3 treatment partially rescued the plant height of the cp-3. Inheritance analysis showed that the cp-3 mutant was regulated via a recessive nuclear locus. A candidate gene, CsERECTA, encoding an LRR receptor-like serine/threonine-protein kinase, was cloned through a map-based cloning strategy. Sequence analysis showed that a nucleotide mutation (C ~ T) in exon 26 of CsERECTA led to premature termination of the protein. Subsequently, two transgenic lines were generated using the CRISPR/Cas9 system, and they showed plant dwarfing. Plant endogenous hormones quantitative and RNA-sequencing analysis revealed that GA3 content and the expression levels of genes related to GA biosynthesis were significantly reduced in Cser knockout mutants. Meanwhile, exogenous GA3 treatment partially rescued the dwarf phenotype of Cser knockout mutants. These findings revealed that CsERECTA controls stem elongation by regulating GA biosynthesis in cucumber.

Oryza CLIMtools: A genome-environment association resource reveals adaptive roles for heterotrimeric G proteins in the regulation of rice agronomic traits

Modern crop varieties display a degree of mismatch between their current distributions and the suitability of the local climate for their productivity. To address this issue, we present Oryza CLIMtools (https://gramene.org/CLIMtools/oryza_v1.0/), the first resource for pan-genome prediction of climate-associated genetic variants in a crop species. Oryza CLIMtools consists of interactive web-based databases that enable the user to (1) explore the local environments of traditional rice varieties (landraces) in South-East Asia and (2) investigate the environment by genome associations for 658 Indica and 283 Japonica rice landrace accessions collected from georeferenced local environments and included in the 3K Rice Genomes Project. We demonstrate the value of these resources by identifying an interplay between flowering time and temperature in the local environment that is facilitated by adaptive natural variation in OsHD2 and disrupted by a natural variant in OsSOC1. Prior quantitative trait locus analysis has suggested the importance of heterotrimeric G proteins in the control of agronomic traits. Accordingly, we analyzed the climate associations of natural variants in the different heterotrimeric G protein subunits. We identified a coordinated role of G proteins in adaptation to the prevailing potential evapotranspiration gradient and revealed their regulation of key agronomic traits, including plant height and seed and panicle length. We conclude by highlighting the prospect of targeting heterotrimeric G proteins to produce climate-resilient crops.

A mutation in CsDWF7 gene encoding a delta7 sterol C-5(6) desaturase leads to the phenotype of super compact in cucumber (Cucumis sativus L.)

KEY MESSAGE

A novel super compact mutant, scp-3, was identified using map-based cloning in cucumber. The CsDWF7 gene encoding a delta7 sterol C-5(6) desaturase was the candidate gene of scp-3. Mining dwarf genes is important in understanding stem growth in crops. However, only a small number of dwarf genes have been cloned or characterized. Here, we characterized a cucumber (Cucumis sativus L.) dwarf mutant, super compact 3 (scp-3), which displays shortened internodes and dark green leaves with a wrinkled appearance. The photosynthetic rate of scp-3 is significantly lower than that of the wild type. The dwarf phenotype of scp-3 mutant can be partially rescued by the exogenous brassinolide (BL) application, and the endogenous brassinosteroids (BRs) levels in the scp-3 mutant were significantly lower compared to the wild type. Microscopic examination revealed that the reduced internode length in scp-3 resulted from a decrease in cell size. Genetic analysis showed that the dwarf phenotype of scp-3 was controlled by a single recessive gene. Combined with bulked segregant analysis and map-based cloning strategy, we delimited scp-3 locus into an 82.5 kb region harboring five putative genes, but only one non-synonymous mutation (A to T) was discovered between the mutant and its wild type in this region. This mutation occurred within the second exon of the CsGy4G017510 gene, leading to an amino acid alteration from Leu156 to His156. This gene encodes the CsDWF7 protein, an analog of the Arabidopsis DWF7 protein, which is known to be involved in the biosynthesis of BRs. The CsDWF7 protein was targeted to the cell membrane. In comparison to the wild type, scp-3 exhibited reduced CsDWF7 expression in different tissues. These findings imply that CsDWF7 is essential for both BR biosynthesis as well as growth and development of cucumber plants.

Oryza CLIMtools: A Genome-Environment Association Resource Reveals Adaptive Roles for Heterotrimeric G Proteins in the Regulation of Rice Agronomic Traits

Modern crop varieties display a degree of mismatch between their current distributions and the suitability of the local climate for their productivity. To this end, we present Oryza CLIMtools (https://gramene.org/CLIMtools/oryza_v1.0/), the first resource for pan-genome prediction of climate-associated genetic variants in a crop species. Oryza CLIMtools consists of interactive web-based databases that allow the user to: i) explore the local environments of traditional rice varieties (landraces) in South-Eastern Asia, and; ii) investigate the environment by genome associations for 658 Indica and 283 Japonica rice landrace accessions collected from georeferenced local environments and included in the 3K Rice Genomes Project. We exemplify the value of these resources, identifying an interplay between flowering time and temperature in the local environment that is facilitated by adaptive natural variation in OsHD2 and disrupted by a natural variant in OsSOC1. Prior QTL analysis has suggested the importance of heterotrimeric G proteins in the control of agronomic traits. Accordingly, we analyzed the climate associations of natural variants in the different heterotrimeric G protein subunits. We identified a coordinated role of G proteins in adaptation to the prevailing Potential Evapotranspiration gradient and their regulation of key agronomic traits including plant height and seed and panicle length. We conclude by highlighting the prospect of targeting heterotrimeric G proteins to produce crops that are climate resilient.

Heat shock-inducible clonal analysis reveals the stepwise establishment of cell fate in the rice stem

The stem, consisting of nodes and internodes, is the shoot axis, which supports aboveground organs and connects them to roots. In contrast to other organs, developmental processes of the stem remain elusive, especially those initiating nodes and internodes. By introducing an intron into the Cre recombinase gene, we established a heat shock-inducible clonal analysis system in a single binary vector and applied it to the stem in the flag leaf phytomer of rice (Oryza sativa). With detailed characterizations of stem structure and development, we show that cell fate acquisition for each domain of the stem occurs stepwise. Cell fate for a single phytomer was established in the shoot apical meristem (SAM) by one plastochron before leaf initiation. Cells destined for the foot (nonelongating domain at the stem base) also started emerging before leaf initiation. Cell fate acquisition for the node began just before leaf initiation at the flank of the SAM, separating cell lineages for leaves and stems. Subsequently, cell fates for the axillary bud were established in early leaf primordia. Finally, cells committed to the internode emerged from, at most, a few cell tiers of the 12- to 25-cell stage stem epidermis. Thus, internode cell fate is established last during stem development. This study provides the groundwork to unveil underlying molecular mechanisms in stem development and a valuable tool for clonal analysis, which can be applied to various species.

Genome-Wide Association Study Identifies a Plant-Height-Associated Gene OsPG3 in a Population of Commercial Rice Varieties

Plant height is one of the most crucial components of plant structure. However, due to its complexity, the genetic architecture of rice plant height has not been fully elucidated. In this study, we performed a genome-wide association study (GWAS) to determine rice plant height using 178 commercial rice varieties and identified 37 loci associated with rice plant height (LAPH). Among these loci, in LAPH2, we identified a polygalacturonase gene, OsPG3, which was genetically and functionally associated with rice plant height. The rice plant exhibits a super dwarf phenotype when the knockout of the OsPG3 gene occurs via CRISPR-Cas9 gene-editing technology. RNA-Seq analysis indicated that OsPG3 modulates the expression of genes involved in phytohormone metabolism and cell-wall-biosynthesis pathways. Our findings suggest that OsPG3 plays a vital role in controlling rice plant height by regulating cell wall biosynthesis. Given that rice architecture is one of the most critical phenotypes in rice breeding, OsPG3 has potential in rice's molecular design breeding toward an ideal plant height.

Evolution of flowering time genes in rice: From the paleolithic to the anthropocene

The evolutionary paths of humans and plants have crossed more than once throughout millennia. While agriculture contributed to the evolution of societies in prehistory, human selection of desirable traits contributed to the evolution of crops during centuries of cultivation. Among cereal crops, rice is currently grown around the globe and represents staple food for almost half of the world population. Over time, rice cultivation has expanded from subtropical to temperate regions thanks to artificial selection of mutants with impaired response to photoperiod. Additional regulatory mechanisms control flowering in response to diverse environmental cues, anticipating or delaying the floral transition to produce seeds in more favourable conditions. Nevertheless, the changing climate is threatening grain production because modern cultivars are sensitive to external fluctuations that go beyond their physiological range. One possibility to guarantee food production could be the exploitation of novel varieties obtained by crossing highly productive Asian rice with stress tolerant African rice. This review explores the genetic basis of the key traits that marked the long journey of rice cultivation from the end of the paleolithic to the anthropocene, with a focus on heading date. By 2050, will rice plants of the future flower in the outer space?

Genetic basis controlling rice plant architecture and its modification for breeding

The shoot and root system architectures are fundamental for crop productivity. During the history of artificial selection of domestication and post-domestication breeding, the architecture of rice has significantly changed from its wild ancestor to fulfil requirements in agriculture. We review the recent studies on developmental biology in rice by focusing on components determining rice plant architecture; shoot meristems, leaves, tillers, stems, inflorescences and roots. We also highlight natural variations that affected these structures and were utilized in cultivars. Importantly, many core regulators identified from developmental mutants have been utilized in breeding as weak alleles moderately affecting these architectures. Given a surge of functional genomics and genome editing, the genetic mechanisms underlying the rice plant architecture discussed here will provide a theoretical basis to push breeding further forward not only in rice but also in other crops and their wild relatives.

Upgrading the genome of an elite japonica rice variety Kongyu 131 for lodging resistance improvement

Developing a new rice variety requires tremendous efforts and years of input. To improve the defect traits of the excellent varieties becomes more cost and time efficient than breeding a completely new variety. Kongyu 131 is a high-performing japonica variety with early maturity, high yield, wide adaptability and cold resistance, but the poor-lodging resistance hinders the industrial production of Kongyu 131 in the Northeastern China. In this study, we attempted to improve the lodging resistance of Kongyu 131 from perspectives of both gene and trait. On the one hand, by QTL analysis and fine mapping we discovered the candidate gene loci. The following CRISPR/Cas9 and transgenic complementation study confirmed that Sd1 dominated the lodging resistance and favourable allele was mined for precise introduction and improvement. On the other hand, the Sd1 allelic variant was identified in Kongyu 131 by sequence alignment, then introduced another excellent allelic variation by backcrossing. Then, the two new resulting Kongyu 131 went through the field evaluation under different environments, planting densities and nitrogen fertilizer conditions. The results showed that the plant height of upgraded Kongyu 131 was 17%-26% lower than Kongyu 131 without penalty in yield. This study demonstrated a precise and targeted way to update the rice genome and upgrade the elite rice varieties by improving only a few gene defects from the perspective of breeding.

Potentially Useful Dwarfing or Semi-dwarfing Genes in Rice Breeding in Addition to the sd1 Gene

The "Green revolution" gene sd1 has been used widely in the breeding of modern rice varieties for over half a century. The application of this gene has increased rice yields and thereby supported a significant proportion of the global population. The use of a single gene, however, has raised concerns in the scientific community regarding its durability, especially given the bottleneck in genetic background and the need for large input of fertilizer. New dwarfing or semi-dwarfing genes are needed to alleviate our dependence on the sole "Green revolution" gene. In the past few years, several new dwarfing and semi-dwarfing genes as well as their mutants have been reported. Here, we provide an extensive review of the recent discoveries concerning newly identified genes that are potentially useful in rice breeding, including methods employed to create and effectively screen new rice mutants, the phenotypic characteristics of the new dwarfing and semi-dwarfing mutants, potential values of the new dwarfing and semi-dwarfing genes in rice breeding, and potential molecular mechanisms associated with the newly identified genes.

Rice OsUBR7 modulates plant height by regulating histone H2B monoubiquitination and cell proliferation

Plant height is an important agronomic trait for lodging resistance and yield. Here, we report a new plant-height-related gene, OsUBR7 in rice (Oryza sativa L.); knockout of OsUBR7 caused fewer cells in internodes, resulting in a semi-dwarf phenotype. OsUBR7 encodes a putative E3 ligase containing a plant homeodomain finger and a ubiquitin protein ligase E3 component N-recognin 7 (UBR7) domain. OsUBR7 interacts with histones and monoubiquitinates H2B (H2Bub1) at lysine148 in coordination with the E2 conjugase OsUBC18. OsUBR7 mediates H2Bub1 at a number of chromatin loci for the normal expression of target genes, including cell-cycle-related and pleiotropic genes, consistent with the observation that cell-cycle progression was suppressed in the osubr7 mutant owing to reductions in H2Bub1 and expression levels at these loci. The genetic divergence of OsUBR7 alleles among japonica and indica cultivars affects their transcriptional activity, and these alleles may have undergone selection during rice domestication. Overall, our results reveal a novel mechanism that mediates H2Bub1 in plants, and UBR7 orthologs could be utilized as an untapped epigenetic resource for crop improvement.

Genome-edited ATP BINDING CASSETTE B1 transporter SD8 knockouts show optimized rice architecture without yield penalty

This study reports the identification of the rice open reading frame Semi-Dwarf in chr8 (SD8) that encodes a putative ortholog of Arabidopsis thaliana ABCB1. Genome editing of SD8 leads to optimized rice architecture by reducing plant height and flag-leaf angle without yield penalty. Rice SD8 knockouts may also have the potential for increased yield under high density planting.

The α subunit of the heterotrimeric G protein regulates mesophyll CO2 conductance and drought tolerance in rice

Mesophyll conductance g_m determines CO₂ diffusion rates from mesophyll intercellular air spaces to the chloroplasts and is an important factor limiting photosynthesis. Increasing g_m in cultivated plants is a potential strategy to increase photosynthesis and intrinsic water use efficiency (WUE_i ). The anatomy of the leaf and metabolic factors such as aquaporins and carbonic anhydrases have been identified as important determinants of g_m . However, genes involved in the regulation and modulation of g_m remain largely unknown. In this work, we investigated the role of heterotrimeric G proteins in g_m and drought tolerance in rice d1 mutants, which harbor a null mutation in the Gα subunit gene, RGA1. d1 mutants in both cv Nipponbare and cv Taichung 65 exhibited increased g_m , fostering improvement in photosynthesis, WUE_i , and drought tolerance compared with wild-type. The increased surface area of mesophyll cells and chloroplasts exposed to intercellular airspaces and the reduced cell wall and chloroplast thickness in the d1 mutant are evident contributors to the increase in g_m . Our results indicate that manipulation of heterotrimeric G protein signaling has the potential to improve crop WUE_i and productivity under drought.

Will Plant Genome Editing Play a Decisive Role in "Quantum-Leap" Improvements in Crop Yield to Feed an Increasing Global Human Population?

Growing scientific evidence demonstrates unprecedented planetary-scale human impacts on the Earth's system with a predicted threat to the existence of the terrestrial biosphere due to population increase, resource depletion, and pollution. Food systems account for 21-34% of global carbon dioxide (CO2) emissions. Over the past half-century, water and land-use changes have significantly impacted ecosystems, biogeochemical cycles, biodiversity, and climate. At the same time, food production is falling behind consumption, and global grain reserves are shrinking. Some predictions suggest that crop yields must approximately double by 2050 to adequately feed an increasing global population without a large expansion of crop area. To achieve this, "quantum-leap" improvements in crop cultivar productivity are needed within very narrow planetary boundaries of permissible environmental perturbations. Strategies for such a "quantum-leap" include mutation breeding and genetic engineering of known crop genome sequences. Synthetic biology makes it possible to synthesize DNA fragments of any desired sequence, and modern bioinformatics tools may hopefully provide an efficient way to identify targets for directed modification of selected genes responsible for known important agronomic traits. CRISPR/Cas9 is a new technology for incorporating seamless directed modifications into genomes; it is being widely investigated for its potential to enhance the efficiency of crop production. We consider the optimism associated with the new genetic technologies in terms of the complexity of most agronomic traits, especially crop yield potential (Yp) limits. We also discuss the possible directions of overcoming these limits and alternative ways of providing humanity with food without transgressing planetary boundaries. In conclusion, we support the long-debated idea that new technologies are unlikely to provide a rapidly growing population with significantly increased crop yield. Instead, we suggest that delicately balanced humane measures to limit its growth and the amount of food consumed per capita are highly desirable for the foreseeable future.

GWAS reveal a role for the central nervous system in regulating weight and weight change in response to exercise

Body size and weight show considerable variation both within and between species. This variation is controlled in part by genetics, but also strongly influenced by environmental factors including diet and the level of activity experienced by the individual. Due to the increasing obesity epidemic in much of the world, there is considerable interest in the genetic factors that control body weight and how weight changes in response to exercise treatments. Here, we address this question in the Drosophila model system, utilizing 38 strains of the Drosophila Genetics Reference Panel. We use GWAS to identify the molecular pathways that control weight and weight changes in response to exercise. We find that there is a complex set of molecular pathways controlling weight, with many genes linked to the central nervous system (CNS). The CNS also plays a role in the weight change with exercise, in particular, signaling from the CNS. Additional analyses revealed that weight in Drosophila is driven by two factors, animal size, and body composition, as the amount of fat mass versus lean mass impacts the density. Thus, while the CNS appears to be important for weight and exercise-induced weight change, signaling pathways are particularly important for determining how exercise impacts weight.

A GPAT1 Mutation in Arabidopsis Enhances Plant Height but Impairs Seed Oil Biosynthesis

Glycerol-3-phosphate acyltransferases (GPATs) play an important role in glycerolipid biosynthesis, and are mainly involved in oil production, flower development, and stress response. However, their roles in regulating plant height remain unreported. Here, we report that Arabidopsis GPAT1 is involved in the regulation of plant height. GUS assay and qRT-PCR analysis in Arabidopsis showed that GPAT1 is highly expressed in flowers, siliques, and seeds. A loss of function mutation in GPAT1 was shown to decrease seed yield but increase plant height through enhanced cell length. Transcriptomic and qRT-PCR data revealed that the expression levels of genes related to gibberellin (GA) biosynthesis and signaling, as well as those of cell wall organization and biogenesis, were significantly upregulated. These led to cell length elongation, and thus, an increase in plant height. Together, our data suggest that knockout of GPAT1 impairs glycerolipid metabolism in Arabidopsis, leading to reduced seed yield, but promotes the biosynthesis of GA, which ultimately enhances plant height. This study provides new evidence on the interplay between lipid and hormone metabolism in the regulation of plant height.

Melon short internode (CmSi) encodes an ERECTA-like receptor kinase regulating stem elongation through auxin signaling

Plant height is one of the most important agronomic traits that directly determines plant architecture, and compact or dwarf plants can allow for increased planting density and land utilization as well as increased lodging resistance and economic yield. At least four dwarf/semidwarf genes have been identified in different melon varieties, but none of them have been cloned, and little is known about the molecular mechanisms underlying internode elongation in melon. Here, we report map-based cloning and functional characterization of the first semidwarf gene short internode (Cmsi) in melon, which encodes an ERECTA-like receptor kinase regulating internode elongation. Spatial-temporal expression analyses revealed that CmSI exhibited high expression in the vascular bundle of the main stem during internode elongation. The expression level of CmSI was positively correlated with stem length in the different melon varieties examined. Ectopic expression of CmSI in Arabidopsis and cucumber suggested CmSI as a positive regulator of internode elongation in both species. Phytohormone quantitation and transcriptome analysis showed that the auxin content and the expression levels of a number of genes involved in the auxin signaling pathway were altered in the semidwarf mutant, including several well-known auxin transporters, such as members of the ABCB family and PIN-FORMED genes. A melon polar auxin transport protein CmPIN2 was identified by protein-protein interaction assay as physically interacting with CmSI to modulate auxin signaling. Thus, CmSI functions in an auxin-dependent regulatory pathway to control internode elongation in melon. Our findings revealed that the ERECTA family gene CmSI regulates stem elongation in melon through auxin signaling, which can directly affect polar auxin transport.

Analysis of a radiation-induced dwarf mutant of a warm-season turf grass reveals potential mechanisms involved in the dwarfing mutant

Zoysia matrella [L.] Merr. is a widely cultivated warm-season turf grass in subtropical and tropical areas. Dwarf varieties of Z. matrella are attractive to growers because they often reduce lawn mowing frequencies. In this study, we describe a dwarf mutant of Z. matrella induced from the 60Co-γ-irradiated calluses. We conducted morphological test and physiological, biochemical and transcriptional analyses to reveal the dwarfing mechanism in the mutant. Phenotypically, the dwarf mutant showed shorter stems, wider leaves, lower canopy height, and a darker green color than the wild type (WT) control under the greenhouse conditions. Physiologically, we found that the phenotypic changes of the dwarf mutant were associated with the physiological responses in catalase, guaiacol peroxidase, superoxide dismutase, soluble protein, lignin, chlorophyll, and electric conductivity. Of the four endogenous hormones measured in leaves, both indole-3-acetic acid and abscisic acid contents were decreased in the mutant, whereas the contents of gibberellin and brassinosteroid showed no difference between the mutant and the WT control. A transcriptomic comparison between the dwarf mutant and the WT leaves revealed 360 differentially-expressed genes (DEGs), including 62 up-regulated and 298 down-regulated unigenes. The major DEGs related to auxin transportation (e.g., PIN-FORMED1) and cell wall development (i.e., CELLULOSE SYNTHASE1) and expansin homologous genes were all down-regulated, indicating their potential contribution to the phenotypic changes observed in the dwarf mutant. Overall, the results provide information to facilitate a better understanding of the dwarfing mechanism in grasses at physiological and transcript levels. In addition, the results suggest that manipulation of auxin biosynthetic pathway genes can be an effective approach for dwarfing breeding of turf grasses.

Discovery of a Novel Induced Polymorphism in SD1 Gene Governing Semi-Dwarfism in Rice and Development of a Functional Marker for Marker-Assisted Selection

The semi-dwarfing allele, sd1-d, has been widely utilized in developing high-yielding rice cultivars across the world. Originally identified from the rice cultivar Dee-Geo-Woo-Gen (DGWG), sd1-d, derived from a spontaneous mutation, has a 383-bp deletion in the SD1 gene. To date, as many as seven alleles of the SD1 gene have been identified and used in rice improvement, either with a functional single-nucleotide polymorphism (SNP), with insertion–deletions (InDels), or both. Here, we report discovery of a novel SNP in the SD1 gene from the rice genotype, Pusa 1652. Genetic analysis revealed that the inheritance of the semi-dwarfism in Pusa 1652 is monogenic and recessive, but it did not carry the sd1-d allele. However, response to exogenous gibberellic acid (GA₃) application and the subsequent bulked segregant and linkage analyses confirmed that the SD1 gene is involved in the plant height reduction in Pusa 1652. Sequencing of the SD1 gene from Pusa 1652 revealed a novel transition in exon 3 (T/A) causing a nonsense mutation at the 300th codon. The stop codon leads to premature termination, resulting in a truncated protein of OsGA20ox2 obstructing the GA₃ biosynthesis pathway. This novel recessive allele, named sd1-bm, is derived from Bindli Mutant 34 (BM34), a γ-ray induced mutant of a short-grain aromatic landrace, Bindli. BM34 is the parent of an aromatic semi-dwarf cultivar, Pusa 1176, from which Pusa 1652 is derived. The semi-dwarfing allele, sd1-bm, was further validated by developing a derived cleaved amplified polymorphic sequence (dCAPS) marker, AKS-sd1. This allele provides an alternative to the most widely used sd1-d in rice improvement programs and the functional dCAPS marker will facilitate marker-assisted introgression of the semi-dwarf trait into tall genotypes.

Differential Physiological Responses Elicited by Ancient and Heritage Wheat Cultivars Compared to Modern Ones

Although ancient, heritage, and modern wheat varieties appear rather similar from a nutritional point of view, having a similar gluten content and a comparable toxicity linked to their undigested gluten peptide, whenever the role of ancient end heritage wheat grains has been investigated in animal studies or in clinical trials, more anti-inflammatory effects have been associated with the older wheat varieties. This review provides a critical overview of existing data on the differential physiological responses that could be elicited in the human body by ancient and heritage grains compared to modern ones. The methodology used was that of analyzing the results of relevant studies conducted from 2010 through PubMed search, by using as keywords “ancient or heritage wheat”, “immune wheat” (protein or peptides), and immune gluten (protein or peptides). Our conclusion is that, even if we do not know exactly which molecular mechanisms are involved, ancient and heritage wheat varieties have different anti-inflammatory and antioxidant proprieties with respect to modern cultivars. It is, therefore, reasonable to assume that the health proprieties attributed to older cultivars could be related to wheat components which have positive roles in the modulation of intestinal inflammation and/or permeability.