The plastochron, the time interval between the formation of two successive leaves, is an important determinant of plant architecture. We genetically and phenotypically investigated many-noded dwarf (mnd) mutants in barley. The mnd mutants exhibited a shortened plastochron and a decreased leaf blade length, and resembled previously reported plastochron1 (pla1), pla2, and pla3 mutants in rice. In addition, the maturation of mnd leaves was accelerated, similar to pla mutants in rice. Several barley mnd alleles were derived from three genes—MND1, MND4, and MND8. Although MND4 coincided with a cytochrome P450 family gene that is a homolog of rice PLA1, we clarified that MND1 and MND8 encode an N-acetyltransferase-like protein and a MATE transporter-family protein, which are respectively orthologs of rice GW6a and maize BIGE1 and unrelated to PLA2 or PLA3. Expression analyses of the three MND genes revealed that MND1 and MND4 were expressed in limited regions of the shoot apical meristem and leaf primordia, but MND8 did not exhibit a specific expression pattern around the shoot apex. In addition, the expression levels of the three genes were interdependent among the various mutant backgrounds. Genetic analyses using the double mutants mnd4mnd8 and mnd1mnd8 indicated that MND1 and MND4 regulate the plastochron independently of MND8, suggesting that the plastochron in barley is controlled by multiple genetic pathways involving MND1, MND4, and MND8. Correlation analysis between leaf number and leaf blade length indicated that both traits exhibited a strong negative association among different genetic backgrounds but not in the same genetic background. We propose that MND genes function in the regulation of the plastochron and leaf growth and revealed conserved and diverse aspects of plastochron regulation via comparative analysis of barley and rice.

A robust symbiotic relationship between soybean and rhizobia can enhance the yield and quality of soybeans by reducing nitrogen fertilizer input, thereby contributing to sustainable agriculture. However, the genetic interplay between soybean cultivars and the rhizobial species colonizing their roots under natural conditions is yet to be sufficiently assessed. In this study, we build on previous observations that have revealed a significant variation in the prevalence of rhizobial species associated with the soybean cultivars “Peking” and “Tamahomare.” Using recombinant inbred lines derived from a cross between Peking and Tamahomare, we performed quantitative trait loci (QTL) analysis of the proportion of Rhizobium species present in the root nodules of these cultivars and accordingly identified a major QTL on chromosome 18, accounting for 42% of the phenotypic variation, which was subsequently localized to a 240‐kb region. RNA‐seq analysis indicated that a single gene harboring nucleotide binding site–leucine‐rich repeat domains exhibited markedly different expression within the QTL region in the parent cultivars. As this locus is distinct from the chromosomal regions containing known nodule‐related genes, such as Rj and rj , we speculate that it represents a novel gene involved in the symbiosis between rhizobia and soybeans. Further research on the function and role of this new gene could potentially contribute to enhancing soybean yield, and hence sustainable agriculture, under low‐nitrogen fertilization conditions.

Rice is the most important crop species in the world, being staple food of more than 80% of people in Asia. About 80% of rice grain is composed of carbohydrates (starch), with its protein content as low as 7–8%. Therefore, increasing the protein content of rice offers way to create a stable protein source that contributes to improving malnutrition and health problems worldwide. We detected two rice lines harboring a significantly higher protein content (namely, HP5-7 and HP7-5) in the EG4 population. The EG4 strain of rice is a unique material in that the transposon mPing has high transpositional activity and high copy numbers under natural conditions. Other research indicated that mPing is abundant in the gene-rich euchromatic regions, suggesting that mPing amplification should create new allelic variants, novel regulatory networks, and phenotypic changes in the EG4 population. Here, we aimed to identify the candidate genes and/or mPing insertion sites causing high protein content by comprehensively identifying the mPing insertion sites and carrying out an RNA-seq-based transcriptome analysis. By utilizing the next-generation sequencing (NGS)-based methods, ca. 570 mPing insertion sites were identified per line in the EG4 population. Our results also indicated that mPing apparently has a preference for inserting itself in the region near a gene, with 38 genes in total found to contain the mPing insertion in the HP lines, of which 21 and 17 genes were specific to HP5-7 and HP7-5, respectively. Transcriptome analysis revealed that most of the genes related to protein synthesis (encoding glutelin, prolamin, and globulin) were up-regulated in HP lines relative to the control line. Interestingly, the differentially expressed gene (DEG) analysis revealed that the expression levels of many genes related to photosynthesis decreased in both HP lines; this suggests the amount of starch may have decreased, indirectly contributing to the increased protein content. The high-protein lines studied here are expected to contribute to the development of high protein-content rice by introducing valuable phenotypic traits such as high and stable yield, disease resistance, and abundant nutrients.

Barley (Hordeum vulgare) is the fourth most highly produced cereal in the world after wheat, rice and maize and is mainly utilized as malts and for animal feed. Barley, a model crop of the tribe Triticeae, is important in comparative analyses of Poaceae. However, molecular understanding about the developmental processes is limited in barley. Our previous work characterized one of two WUSCHEL-RELATED HOMEOBOX 3 (WOX3) genes present in the barley genome: NARROW LEAFED DWARF1 (NLD1). We demonstrated that NLD1 plays a pivotal role in the development of lateral organs. In the present study, we describe a bifurcated palea (bip) mutant of barley focusing on flower and leaf phenotypes. The palea in the bip mutant was split into two and develop towards inside the lemma surrounding the carpels and anthers. The bip mutant is devoid of lodicules, which develop in a pair at the base of the stamen within the lemma in normal barley. bip also exhibited malformations in leaves, such as narrow leaf due to underdeveloped leaf-blade width, and reduced trichome density. Map-based cloning and expression analysis indicated that BIP is identical to another barley WOX3 gene, named HvWOX3. The bip nld1 double mutant presented a more severe reduction in leaf-blade width and number of trichomes. By comparing the phenotypes and gene expression patterns of various WOX3 mutants, we concluded that leaf bilateral outgrowth and trichome development are promoted by both NLD1 and HvWOX3, but that HvWOX3 serves unique and pivotal functions in barley development that differ from those of NLD1.

During vegetative growth, plants undergo various morphological and physiological changes in the transition from the juvenile phase to the adult phase. In terms of stress resistance, it has been suggested that plants gain or reinforce disease resistance during the process of maturation, which is recognized as adult plant resistance or age-related resistance. While much knowledge has been obtained about changes in disease resistance as growth stages progress, knowledge about changes in plant responses to pathogens with progressing age in plants is limited. In this study, we experimentally compared rice blast resistance in rice leaves sampled from plants at different growth phases. The results indicate differential infection progression and fungal status depending on growth stage. Transcriptome analysis following blast fungus infection revealed that several genes involved in the defense response were upregulated in both the juvenile and intermediate stage, but the expression changes of many genes were growth phase-specific. These findings highlight differences in rice leaf stress responses to blast infection at different growth stages.