Biology subjects

Hotta, C. T.

Publications and source records attributed to Hotta, C. T..

7 recordsLinked to original sources

bioRxiv2026

Soybean Growth and Nodulation Under Mars-Like Magnesium Sulfate Concentrations

Colonising Mars requires sustainable food production systems that use local resources. However, the Martian regolith presents significant challenges for plant cultivation. We investigated whether soybean (Glycine max (L.) Merr.) could grow and form symbiotic nodules with Bradyrhizobium japonicum in MGS-1, a high-fidelity Martian regolith simulant. Soybean plants grown in an MGS-1:vermiculite mix (1:2) and supplemented with a nutrient solution were shorter, produced fewer leaves, and accumulated less biomass than sand-grown plants. More importantly, no nodulation occurred in MGS-1, despite successful nodulation in sand-grown controls. To identify factors inhibiting nodulation, we tested increasing concentrations of MgSO4; (50-150 mM), a major salt in MGS-1, and osmotic stress (300 mM Mannitol). While both treatments reduced nodule numbers, nodulation persisted across all MgSO4; concentrations and under osmotic stress, indicating that neither factor fully accounts for the absence of nodules in MGS-1. The shoot-to-root dry weight ratio increased under MgSO4; stress but decreased under mannitol, suggesting distinct stress responses. Our findings demonstrate that soybean can survive in MGS-1 with nutrient supplementation and an additional substrate to improve MGS-1 compactness and porosity. Still, soybean grown in MGS-1 exhibits severe developmental constraints and complete inhibition of biological nitrogen fixation. Overcoming these limitations will require strategies to mitigate salinity, alkalinity, and physical compaction, as well as engineering symbiotic conditions compatible with sustainable agriculture on Mars.

plant biology↗

bioRxiv2026

Timing of transient darkness shapes carbon-nitrogen metabolism and sugar signaling in sugarcane

Fluctuating light is common in field environments. Yet, the mechanisms by which C4 crops coordinate carbon and nitrogen metabolism during short-term carbon deprivation remain poorly understood. Here, we imposed transient darkness at different phases of the diel cycle to assess how the timing of light loss affects photosynthesis, carbohydrate turnover, amino acid dynamics, and sugar-sensing pathways in commercial sugarcane leaves. Early-day darkness significantly impaired photosynthetic induction and revealed a temporal disconnect between stomatal and metabolic limitations, whereas midday and late-day treatments caused temporary, time-specific disruptions in carbon assimilation. These shifts altered the balance between sucrose preservation and catabolic mobilization, leading to treatment-dependent changes in starch reserves and free amino acids. Core circadian components largely maintained their phase relationships, but their amplitudes varied across treatments, consistent with partial decoupling from carbon status. Darkness also reorganized energy signaling, with SnRK1 and DIN6 responses associated with greater declines in sucrose. Notably, trehalose-pathway transcripts showed marked changes in network connectivity, with ScTPSIIG consistently emerging as a highly connected candidate associated with photosynthetic performance, water-use traits, sugar sensing, and amino acid metabolism. Overall, these results indicate that the timing of carbon limitation and residual sucrose availability shape distinct metabolic responses, while trehalose metabolism provides a candidate regulatory layer coordinating carbon-nitrogen adjustment during the diel cycle, highlighting class II TPS proteins as targets for functional investigation of metabolic resilience in sugarcane.

plant biology↗

bioRxiv2025

Mass Spectrometry-Based Characterization of Histone Post-Translational Modifications in Sugarcane

Histones, the core components of nucleosomes, play an important role in chromatin structure and function through post-translational modifications (PTMs) that regulate gene expression without altering the DNA sequence. Sugarcane (Saccharum spp.), a highly polyploid and economically significant crop, has a complex genome with a limited understanding of histone PTMs. In this study, we employed mass spectrometry to characterise the PTMs of histones in internodes of field-grown commercial sugarcane, harvested at different times of the day, with a focus on histones H2A and H2B, which had not been previously studied in this context. Using a sorghum histone catalog as a reference, we identified 26 H1, 91 H2A, 70 H2B, 5 CENH3, 36 H3.1, 23 H3.3, 18 H3.3L, and 57 H4 loci in the sugarcane genome. We detected extensive PTMs, including acetylation and methylation, across histones H2A, H2B, H3, and H4. Canonical and variant histones showed distinct post-translational modification (PTM) patterns, highlighting their functional specialisation. This study provides a comprehensive catalog of sugarcane histone PTMs, offering insights into their roles in chromatin dynamics and gene regulation, with potential applications in crop improvement and stress adaptation.

plant biology↗

bioRxiv2021

Field microenvironments regulate crop diel transcript and metabolite rhythms

O_LIMost research in plant chronobiology was done in laboratory conditions. However, they usually fail to mimic natural conditions and their slight fluctuations, highlighting or obfuscating rhythmicity. High-density crops, such as sugarcane (Saccharum hybrid), generate field microenvironments with specific light and temperature due to mutual shading. C_LIO_LIWe measured the metabolic and transcriptional rhythms in the leaves of 4-month-old (4 mo) and 9 mo sugarcane grown in the field. Most of the assayed rhythms in 9 mo sugarcane peaked >1 h later than in 4 mo sugarcane, including rhythms of the circadian clock gene, LATE ELONGATED HYPOCOTYL (LHY). C_LIO_LIWe hypothesized that older sugarcane perceives dawn later than younger sugarcane due to self-shading. As a test, we measured LHY rhythms in plants on the east and the west side of a field. We also tested if a wooden wall built between lines of sugarcane changed their rhythms. The LHY peak was delayed in the plants in the west of the field or beyond the wall; both shaded at dawn. C_LIO_LIWe conclude that plants in the same field may have different phases due to field microenvironments, impacting important agronomical traits, such as flowering time, stalk weight and number. C_LI

plant biology↗

bioRxiv2020

L-DOPA dioxygenase of the fly agaric toadstool: revision of the dodA gene sequence and mechanism of enzymatic pigment production

O_SCPLOWLC_SCPLOW-DOPA extradiol dioxygenases (DODAs) catalyze the production of betalains and hygroaurins pigments. The sequence of the DODAs found in Caryophyllales and Basidiomycetes are not conserved, although betalains are produced both by plants and fungi. Here we revise the coding region of the dodA gene of fly agaric [Amanita muscaria (L.) Lam.] and describe an alternative start codon downstream that enables the heterologous expression of AmDODA, a promiscuous O_SCPLOWLC_SCPLOW-DOPA dioxygenase. AmDODA is 43-amino acid residues shorter than the recombinant DODA previously reported but catalyzes the formation of two isomeric seco-DOPAs that are the biosynthetic precursors of betalains and hygroaurins. The putative active site of AmDODA contains two distinct His-His-Glu motifs that can explain the dual cleavage of O_SCPLOWLC_SCPLOW-DOPA according to the mechanism proposed for non-heme iron-dependent dioxygenases. Upon addition of excess O_SCPLOWLC_SCPLOW-DOPA, both the betaxanthin and hygroaurin adducts of O_SCPLOWLC_SCPLOW-DOPA are produced. The kinetic parameters of enzymatic catalysis at pH 8.5 are similar to those reported for other O_SCPLOWLC_SCPLOW-DOPA dioxygenases. The rate constants for the conversion of O_SCPLOWLC_SCPLOW-DOPA into the betalamic acid and muscaflavin were estimated by kinetic modelling allowing the proposal of a mechanism of pigment formation. These results contribute to understanding the biosynthesis of bacterial, fungal and plant pigments, for the biotechnological production of hygroaurins, and for the development of more promiscuous dioxygenases for environmental remediation.

biochemistry↗

bioRxiv2019

Alternative splicing of circadian clock genes is temperature regulated in field-grown sugarcane

Alternative Splicing (AS) is a mechanism that generates different mature transcripts from precursor mRNAs (pre-mRNAs) of the same gene. In plants, a wide range of physiological and metabolic events are related to AS, as well as fast responses to changes in temperature. AS is present in around 60% of intron-containing genes in Arabidopsis, 46% in rice and 38% in maize and it is widespread among the circadian clock genes. Little is known about how AS influences the circadian clock of C4 plants, like commercial sugarcane, a C4 crop with a complex hybrid genome. This work aims to test if the daily dynamics of AS forms of circadian clock genes are regulated by environmental factors, such as temperature, in the field. A systematic search for AS in five sugarcane clock genes, ScLHY, ScPRR37, ScPRR73, ScPRR95 and ScTOC1 using different organs of sugarcane sampled during winter, with 4 months old plants, and during summer, with 9 months old plants, revealed temperature- and organ-dependent expression of at least one alternatively spliced isoform in all genes. Expression of AS isoforms varied according to the season. Our results suggest that AS events in circadian clock genes are correlated with temperature.

plant biology↗

bioRxiv2019

Rhythms of Transcription in Field-Grown Sugarcane Are Highly Organ Specific

We investigated whether different specialized organs in field-grown sugarcane follow the same temporal rhythms in transcription. We assayed the transcriptomes of three organs during the day: leaf, a source organ; internodes 1 and 2, sink organs focused on cell division and elongation; and internode 5, a sink organ focused on sucrose storage. The leaf had twice as many rhythmic transcripts (>68%) as internodes, and the rhythmic transcriptomes of the two internodes were more similar to each other than to those of the leaves. More transcripts were rhythmic under field conditions than under circadian conditions and most of their peaks were during the day. Among the transcripts that were considered expressed in all three organs, only 7.4% showed the same rhythmic time course pattern. The central oscillators of these three organs -- the networks that generate circadian rhythms -- had similar dynamics with different amplitudes. The differences between the rhythmic transcriptomes in circadian conditions and field conditions highlight the importance of field experiments to understand the plant circadian clock in natura. The highly specialized nature of the rhythmic transcriptomes in sugarcane organs probably arises from amplitude differences in tissue-specific circadian clocks and different sensitivities to environmental cues. One sentence summaryThe rhythmic transcriptome of field-grown sugarcane is highly organ-specific.

plant biology↗