Soluble oxalate accumulates in rice leaves, and it causes mineral deficiency and urinary syndrome in livestock that consume the leaves. In our previous study, we found that the oxalate content was higher in the leaves of Koshihikari (japonica type cultivar) than in those of Takanari (indica type cultivar). This difference was seen even when the two cultivars were grown under a high CO₂ concentration, which inhibits oxalate synthesis via photorespiration, suggesting that the difference resulted from genetic factors rather than environmental factors. To clarify whether genetic factors affect the oxalate content of rice leaves, we measured the contents of oxalate and oxalate-related organic acids in the leaves of various rice cultivars the Rice Core Collection (WRC) and Japan Rice Core Collection (JRC) by capillary electrophoresis-mass spectrometry. Results showed that japonica type cultivars tended to accumulate more oxalate than aus or indica type cultivars. Correlation analysis revealed a positive correlation between oxalate accumulation and the citrate content, suggesting that the isocitrate pathway is involved in oxalate accumulation. On the other hand, a genome-wide association study for the oxalate content of the WRC and JRC cultivars did not reveal significant loci directly related to oxalate accumulation. This indicates that the combination of various loci may affect the oxalate contents of rice leaves.

Accumulation of anthocyanin provides pigmentation in plant tissues. In petunia, gene expression profiles that lead to anthocyanin production have been extensively characterized in terms of pigmentation in flower petals. Anthers are also pigmented, but the transcriptional control of the genes for anthocyanin biosynthesis in anthers has not been fully characterized. Here we addressed this issue by analyzing the expression of structural genes and genes encoding transcription factors (TFs) of the pathway. Ectopic expression of the PURPLE HAZE (PHZ) gene encoding an R2R3-MYB activator induced pigmentation in anthers. The pigmentation was accompanied by an increase in mRNA levels of AN1, MYB27 and MYBx among the genes encoding TFs. Among the structural genes, mRNA levels of four late biosynthetic genes (LBGs) were higher in the transformants than in the wild type. Analyses of gene expression profile using commercial varieties indicated that mRNA levels of MYB27, MYBx and LBGs and of AN4, responsible for anther pigmentation, were higher in pigmented anthers than in nonpigmented. Differences in the gene expression profile between pigmented anthers induced by ectopic PHZ expression and their nonpigmented control and those between pigmented anthers and nonpigmented anthers of existing varieties were thus remarkably similar. These observations suggest that a high level of expression of the LBGs is characteristic of pigmented anthers and that ectopic PHZ expression in the an4⁻ genetic background induced changes in the transcriptional network toward the state established in pigmented anthers, which is intrinsically brought about by the function of AN4.

Stomatal regulation, a multifaceted mechanism enabling plants to adapt to diverse environmental conditions and optimize photosynthesis for survival and growth, is considered crucial in drought stress tolerance research. To further enhance our understanding of stomatal regulation, we investigated the novel transcription factors involved in this process. Our findings reveal that SHOOT GRAVITROPISM 5 (SGR5) is involved in the stomatal response to darkness in Arabidopsis. Water loss measurements showed that SGR5-overexpressing plants retained more water, whereas SGR5-knockout lines exhibited increased water loss compared with the control. Unexpectedly, our analyses indicated that SGR5 was not associated with the abscisic acid signaling pathway, in contrast to its homologous transcription factor, INDETERMINATE DOMAIN 14. Instead, SGR5-knockout lines exhibited weakened stomatal closure responses upon transition to darkness. Collectively, our results highlight the regulatory role of SGR5 in mediating stomatal movement in response to darkness.

Candidatus Liberibacter asiaticus (CLas), a phloem-limited Gram-negative bacterium, is associated with citrus huanglongbing (HLB), which is one of the most destructive diseases currently threatening citrus production worldwide. No effective treatment for HLB is currently available. Effective prevention and control in the initial stage can block the spread and disease progression of HLB. Herein, we developed a co-detection assay for the 16S rDNA and 16S rRNA of CLas, the sensitivity of the co-detection assay was significantly increased over that of the single CLas DNA detection system. Beyond this, we found that the co-detection assay was a better fit to the root samples with higher population abundance than the previous reported detection system because it has a better specificity. Moreover, we found that the contents of 16S rRNA of CLas in citrus roots and fruits are significantly higher than that in leaves, which suggests that the time of HLB diagnosis is probably earlier by using these special tissues and the replication of CLas may become more active in these tissues, further suggested that the significance of study the mechanism of infection, prevention and control of HLB staring from these tissues.

SNAREs play an important role in the process of membrane trafficking. In the present research, we investigated subcellular localization of an uncharacterized Arabidopsis thaliana protein reported to interact with a trans-Golgi network-localized Qa-SNARE, SYNTAXIN OF PLANTS 43. Based on the similarity of its amino acid sequence to metazoan fucosyltransferases, we have named this novel protein AtGTLP (Arabidopsis thaliana GlycosylTransferase-Like Protein) and predicted that it should be a member of yet uncharacterized family of Arabidopsis fucosyltransferases, as it shows no significant sequence similarity to fucosyltransferases previously identified in Arabidopsis. AtGTLP is a membrane-anchored protein, which exhibits a type II-like topology, with a single transmembrane helix and a globular domain in the C-terminal part of its amino acid sequence. Colocalization data we collected suggest that AtGTLP should localize mainly to Golgi apparatus, especially to certain zones of trans-Golgi. As single atgtlp−/− mutants showed no obvious difference in phenotype (primary root length and fresh mass), AtGTLP and proteins related to AtGTLP with high similarity in amino acid sequences may have redundant functions.

Date palm (Phoenix dactylifera L.) is a dioecious plant, with male and female plants having distinct characteristics. Female plants are responsible for fruit production, and only approximately 10% of male plants are necessary for effective pollination. The determination of plant sex occurs during the first flowering, a process that typically spans 3–7 years. However, this extended timeframe results in significant time and valuable plantation resources being expended in the maintenance of trees. To address this issue, the study focused on sex identification of date palms using DNA markers. The research aimed to develop sex-specific markers for certain date palm cultivars, employing the high annealing temperature random amplified polymorphic DNA (HAT-RAPD) technique for accurate and reliable sex identification. In this investigation, 45 RAPD primers underwent screening in both male and female date palm plants to pinpoint sex-specific markers. Out of the total primers tested, only one, OPW-18, exhibited a correlation with sex. OPW-18 produced a distinct band of approximately 400 bp, consistently present in all male plants but absent in all female plants. The male-specific fragment from OPW-18 was cloned and sequenced to facilitate the development of sex-specific sequence-characterized amplified region (SCAR) primers. The outcomes revealed that the newly crafted SCAR primer pair, mspW18-2F and mspW18-2R, successfully amplified a unique fragment of 283 bp exclusively in male plants. This capability allowed the identification of 100% of male plants in the KL1 and Barhi cultivars. These markers prove to be efficient, reliable, and reproducible for early-stage sex identification in plants.

Petunia hybrida (Solanaceae) exhibits high sensitivity to water scarcity, especially during flowering. This study investigated changes in the flowering time of P. hybrida in response to water deficit over a 7-week period. Various levels of water stress—i.e., light, moderate, and severe—were imposed on plants grown in a greenhouse, and these were compared to a control group grown alongside. Remarkably, early flowering was observed under severe stress in P. hybrida for the first time, occurring 5.3 days earlier than in the control group. Furthermore, seeds collected from control and treatment plants were then used to assess drought stress memory in offspring. Seedlings were cultivated in a dehydration medium containing either PEG 8000 or a control MS medium. In the PEG 8000 medium, seedlings from parents exposed to moderate and severe drought stresses exhibited higher drought tolerance than those from well-watered conditions. Moreover, they also displayed significantly longer roots, more leaves, and a lower ion leakage rate. Taken together, these findings demonstrated the presence of positive transgenerational effects on progeny. Thus, while parental drought stress during reproduction stage may affect seed quality, it can enhance drought tolerance in the next generation via induction of stress memory.

SABATH proteins methylate the carboxyl groups or nitrogen atoms of small plant molecules and play important roles in many developmental processes and plant defense responses. Previous studies have shown that indole-3-acetic acid (IAA) carboxyl methyltransferase (IAMT), a member of the SABATH methyltransferase family, converts IAA into its methyl ester (Me-IAA). We used RNA-seq analysis to identify a putative IAMT gene, IaIAMT, in the ancient angiosperm Illicium anisatum. Functional characterization of the recombinant IaIAMT protein expressed in Escherichia coli showed the highest level of activity with IAA, whereas indole-3-propionic acid and indole-3-butyric acid were not used as substrates. The apparent K_m value of IaIAMT using IAA as a substrate was determined to be 122 µM. Phylogenetic analysis and structural modeling of IaIAMT suggested that IaIAMT evolved independently from IAMTs isolated from other plant species, whereas strict substrate specificity toward IAA was conserved in Illicium species, as observed in other plants.

Heat stress, which occurs when temperatures exceed the optimal range for growth, challenges the maintenance of crop yield because it disrupts plant homeostasis at the cellular and developmental levels. Chemical priming, which can activate the response to environmental stress using chemical compounds, is a promising method of maintaining plant growth under stressful conditions. Recently, we found that the non-proteogenic amino acid N-acetylglutamic acid (NAG) confers tolerance to oxidative stress through the activation of genes related to scavenging reactive oxygen species in plants. However, it has been unknown whether NAG alleviates environmental stress except oxidative stress. Here, we revealed that the response to heat stress was enhanced by exogenous treatment with NAG in plants. NAG alleviated the reduction in chlorophyll content induced by heat stress in Arabidopsis thaliana. Gene expression analysis showed that NAG activates the transcription factor HSFA2, which is regarded as a master regulator of the transcriptional cascade in response to heat stress. NAG induces histone H4 acetylation, an active histone modification, at the HSFA2 locus, suggesting that NAG could activate the expression of HSFA2 based on epigenetic modifications such as histone acetylation. Additionally, we found that Oryza sativa treated with NAG showed tolerance to heat stress. These results suggest that NAG could be used for chemical priming in the maintenance of plant growth under heat-stress conditions.

Eggplant (Solanum melongena L.) fruits are known to contain few carotenoids such as β-carotene, which are abundant in congener tomato fruits. In a previous study, we introduced a fruit-specific EEF48 gene promoter-driven crtB gene encoding phytoene synthase (PSY) of Erwinia uredovora into eggplant ‘Senryo No. 2’. The transgenic plants grown in a greenhouse set fruits that accumulated β-carotene (∼1.67 µg g⁻¹FW) in the T₀ and T₁ generations. In the present study, we grew T₁ and T₂ generations of the transgenic eggplant plants in artificial climate chambers to investigate their fruit set and β-carotene accumulation. No clear difference in β-carotene accumulation was observed in the fruit of transgenic plants grown under either HID (high-intensity discharge) or LED (light-emitting diode) light, or between T₁ and T₂ generations. The β-carotene accumulation (8.83 µg g⁻¹FW on average) was approximately 5 times higher than the previous results obtained from greenhouse-grown plants. However, the fruit weight and size of the T-DNA (+) plants were significantly smaller than that of their null-segregant T-DNA (−) plants derived from the same line, suggesting that β-carotene accumulation may inhibit fruit development. Considering that a part of plants grown under LED irradiation failed to set fruits or set smaller fruits than those grown under HID irradiation, the light condition in the LED chamber may not be sufficient to promote fruit development. The present results are expected to provide valuable information for the selection of transgenic eggplants with high β-carotene content in fruit under artificial lighting.

Rational metabolic-flow switching is an effective strategy that we proposed for producing exogenous high-value natural products using transformed plant cells. In an earlier proof-of-concept study, we generated bamboo (Phyllostachys nigra; Pn) cells expressing the 4-hydroxycinnamoyl-CoA hydratase/lyase gene of Pseudomonas putida KT2440 (PpHCHL). The encoded enzyme catalyzes the formation of 4-hydroxybenzaldehyde and vanillin from p-coumaroyl-CoA and feruloyl-CoA, respectively. The PpHCHL-transformed Pn cells accumulated mono-glucose conjugates (glucoside and glucose ester) of 4-hydroxybenzoic acid and vanillic acid, indicating that the products (aldehydes) of the PpHCHL-catalyzed reaction were oxidized by endogenous enzyme(s) in Pn cells. In this study, we re-examined the extracts of PpHCHL-transformed Pn cells to screen for additional 4-hydroxybenzoic acid derivatives. An unidentified compound was detected exclusively in the PpHCHL-transformed Pn cells. This compound was purified via column chromatography and then identified as a di-glucose conjugate of 4-hydroxybenzoic acid (i.e., β-D-glucopyranosyl 4-O-β-D-glucopyranosylbenzoate), implying that some of the mono-glucose conjugates of 4-hydroxybenzoic acid were converted to the di-glucose conjugate by endogenous enzyme(s) in Pn cells. The maximum production titer of this di-glucose conjugate in the suspension-cultured cells was 0.38 g l⁻¹, which was the second highest titer among the four glucose conjugates produced by the PpHCHL-transformed Pn cells. The study findings further support the utility of PpHCHL-transformed Pn cells for the bioproduction of 4-hydroxybenzoic acid and its derivatives.