Biology subjects

Ohyama, A.

Publications and source records attributed to Ohyama, A..

3 recordsLinked to original sources

bioRxiv2026

TAB1 and ASP1 act antagonistically on cytokinin signaling to regulate axillary meristem formation in rice

Plants continuously develop shoot branches derived from axillary meristems. In rice (Oryza sativa), TILLERS ABSENT1 (TAB1), an ortholog of Arabidopsis WUSCHEL, plays an essential role in axillary meristem formation by promoting stem cell proliferation. Although several genes associated with TAB1 function have been identified, the molecular mechanisms underlying stem cell proliferation during axillary meristem formation remain poorly understood. Here we identify ABERRANT SPIKELET AND PANICLE1 (ASP1), a TOPLESS-like transcriptional corepressor, as a novel regulator of axillary meristem formation, and investigate downstream mechanisms regulated by TAB1 and ASP1. In asp1, the stem cell region was expanded, indicating that ASP1 negatively regulates stem cell proliferation. Notably, WOX4, a paralog of TAB1, was precociously expressed in asp1, possibly in association with expansion of the stem cell region. Genetic analysis further revealed that asp1 mutation rescued the loss of axillary meristems in tab1. Transcriptome analysis showed that several type-A RESPONSE REGULATOR (OsRR) genes, encoding negative regulators of cytokinin signaling, were upregulated in tab1 relative to wild type, asp1, and the tab1 asp1 double mutant. Consistently, fluorescence of the synthetic cytokinin reporter was absent during axillary meristem formation in tab1 but was detected in wild type and tab1 asp1. Moreover, overexpression of OsRR10 inhibited axillary meristem formation, phenocopying tab1. Collectively, these findings suggest that TAB1 activates cytokinin signaling by repressing type-A OsRR expression, whereas ASP1 negatively regulates cytokinin signaling by promoting the expression of these genes. Thus, rescue of the tab1 phenotype by asp1 mutation probably reflects restoration of cytokinin signaling.

plant biology↗

bioRxiv2026

Circulating miR-1285-3p promotes age-associated B cell differentiation through the OXPHOS-IKZF2 axis in SLE

Age-associated B cells (ABCs) expand in systemic lupus erythematosus (SLE) and contribute to pathogenic humoral immunity, but the mechanisms that restrain their differentiation remain unclear. Here, we identify the transcription factor IKZF2 (Helios) as a regulator that limits ABC differentiation. Transcriptomic and functional analyses showed that suppression of oxidative phosphorylation (OXPHOS) in B cells promoted ABC differentiation and was accompanied by reduced IKZF2 expression. Pharmacologic modulation of mitochondrial metabolism further demonstrated that OXPHOS inhibition promoted, whereas OXPHOS activation restrained, ABC differentiation. Integrative analyses revealed reduced IKZF2 expression in selected B cell subsets from patients with SLE. Functional suppression of IKZF2 enhanced ABC differentiation and attenuated the inhibitory effects of OXPHOS activation, indicating that IKZF2 mediates metabolic control of B cell fate. Mechanistically, IKZF2 restrained early ABC-associated gene programs, including ITGAX and TBX21. Circulating miR-1285-3p in small extracellular vesicles, elevated in SLE, suppressed OXPHOS and recapitulated these effects. Together, these findings identify an OXPHOS-IKZF2 axis that restrains pathogenic B cell differentiation and links extracellular microRNA-mediated metabolic stress to ABC formation in SLE. One-sentence summarySmall EV-associated miR-1285-3p in SLE promotes ABC differentiation by suppressing OXPHOS and relieving IKZF2-mediated restraint.

immunology↗

bioRxiv2023

Identification of major quantitative trait loci for parthenocarpic ability in East Asian melon

Natural (genetic) parthenocarpy contributes to fruit yield and quality under unfavorable environmental conditions where there are no effective pollinators or fertile pollen grains. Several old melon cultivars and weedy melon in East Asia are known to have strong parthenocarpic ability, but there has been little progress in intentionally introducing this ability into current F1 hybrid cultivars. Here, we examined its inheritance and confirmed the selection accuracy of DNA markers linked to it. We conducted QTL analysis using three F2 populations derived from crosses between a non-parthenocarpic cultivar and three parthenocarpic accessions, and detected two major QTLs on chromosomes 2 (par2.1) and 3 (par3.1). The parthenocarpic parent allele at both QTLs enhanced parthenocarpic ability. Phenotypic segregation was well explained by par2.1 and par3.1 in two F2 populations derived from Japanese weedy melon and an old Korean cultivar and by par3.1 in one from an old Japanese cultivar. This difference suggests that the effects of par2.1 and par 3.1 depend on genetic background. Both QTL regions contain several phytohormone-related genes, so we randomly selected SNPs in auxin- and ethylene-related genes to confirm the accuracy of selection for parthenocarpic ability. These SNP markers proved sufficient, though not perfect, to select plants with strong parthenocarpic ability. These results provide new insights into the molecular mechanisms of parthenocarpic ability in melon and will contribute to the development of new cultivars with high parthenocarpic ability. Key messageSeveral oriental melons have strong parthenocarpic ability controlled by one or two loci. DNA markers linked to these loci can select individuals with this ability.

plant biology↗