Vascular plant one-zinc-finger protein 1/2 transcription factors regulate abiotic and biotic stress responses in Arabidopsis.

Plants adapt to abiotic and biotic stresses by activating abscisic acid-mediated (ABA) abiotic stress-responsive and salicylic acid-(SA) or jasmonic acid-mediated (JA) biotic stress-responsive pathways, respectively. Although the abiotic stress-responsive pathway interacts antagonistically with the biotic stress-responsive pathways, the mechanisms that regulate these pathways remain largely unknown. In this study, we provide insight into the function of vascular plant one-zinc-finger proteins (VOZs) that modulate various stress responses in Arabidopsis. The expression of many stress-responsive genes was changed in the voz1voz2 double mutant under normal growth conditions. Consistent with altered stress-responsive gene expression, freezing- and drought-stress tolerances were increased in the voz1voz2 double mutant. In contrast, resistance to a fungal pathogen, Colletotrichum higginsianum, and to a bacterial pathogen, Pseudomonas syringae, was severely impaired. Thus, impairing VOZ function simultaneously conferred increased abiotic tolerance and biotic stress susceptibility. In a chilling stress condition, both the VOZ1 and VOZ2 mRNA expression levels and the VOZ2 protein level gradually decreased. VOZ2 degradation during cold exposure was completely inhibited by the addition of the 26S proteasome inhibitor, MG132, a finding that suggested that VOZ2 degradation is dependent on the ubiquitin/26S proteasome system. In voz1voz2, ABA-inducible transcription factor CBF4 expression was enhanced significantly even under normal growth conditions, despite an unchanged endogenous ABA content. A finding that suggested that VOZs negatively affect CBF4 expression in an ABA-independent manner. These results suggest that VOZs function as both negative and positive regulators of the abiotic and biotic stress-responsive pathways, and control Arabidopsis adaptation to various stress conditions.

Bowen disease on the dorsum of the foot associated with human papillomavirus type 16.

A 94 years old Japanese female was presented to our hospital with a skin lesion on her left foot. A physical examination found a markedly hyperkeratotic reddish-brown plaque, measuring 3 cm in diameter. A biopsy specimen showed prominent papillomatosis, hyperkeratosis, and atypical keratinocytes throughout the epidermis. Individual cell keratinization, multinucleated keratinocytes, and many keratinocytes with clear cytoplasm were seen. We excised the lesion, and the skin grafting was used for covering the skin defect. We investigated whether human papillomavirus (HPV) was present in the lesion, and HPV 16 DNA was detected using the polymerase chain reaction. Immunohistochemical analysis showed several HPV-positive cells in the upper epidermis. In addition, the tumor cells showed strong and diffuse expression of p16INK4a. Bowen disease (BD) is an intraepidermal squamous cell carcinoma. The precise pathogenesis of BD is unclear, but it involves various factors. HPV infection is one of these factors and is a well-known cause of BD of the genitalia and fingers. It has been shown that some BD lesions occurring at other locations are also associated with HPV. Dysregulation of the Rb/p16INK4a pathway is considered to play an important role in HPV-induced BD, but the precise mechanism remains to be elucidated. J. Med. Invest. 69 : 152-154, February, 2022.

Vascular plant one-zinc-finger protein 2 is localized both to the nucleus and stress granules under heat stress in Arabidopsis.

VASCULAR PLANT ONE-ZINC FINGER (VOZ)1/and VOZ2 have an ability to bind to the specific cis-element in the AVP1 promoter of Arabidopsis, which function on the PhyB-dependent flowering and possibly in various stress responses as potential transcription factors, although nuclear localization of VOZ proteins is still unclear. In this study, we found that VOZ2 is dispersed throughout the cytoplasm under normal growth conditions, whereas VOZ2 is transferred not only to the nucleus but also to the cytoplasmic foci under heat stress conditions. The VOZ2 foci predominantly co-localized with a marker of stress granules (SGs), which were cytoplasmic granular structures for mRNA storage and decay under abiotic stress conditions. We also demonstrated that GFP-VOZ2 with a nuclear localization signal was rapidly degraded via the ubiquitin/proteasome pathway under the heat stress conditions. Also, stress-related expression of DREB2A in the voz1voz2 mutant was significantly upregulated by heat stress as compared with that in the wild-type Arabidopsis. Our results suggest that VOZ2 is localized to SGs and nucleus under heat stress conditions, and functions as a transcriptional repressor of DREB2A in Arabidopsis.

Split luciferase complementation assay to detect regulated protein-protein interactions in rice protoplasts in a large-scale format.

BACKGROUND: The rice interactome, in which a network of protein-protein interactions has been elucidated in rice, is a useful resource to identify functional modules of rice signal transduction pathways. Protein-protein interactions occur in cells in two ways, constitutive and regulative. While a yeast-based high-throughput method has been widely used to identify the constitutive interactions, a method to detect the regulated interactions is rarely developed for a large-scale analysis. RESULTS: A split luciferase complementation assay was applied to detect the regulated interactions in rice. A transformation method of rice protoplasts in a 96-well plate was first established for a large-scale analysis. In addition, an antibody that specifically recognizes a carboxyl-terminal fragment of Renilla luciferase was newly developed. A pair of antibodies that recognize amino- and carboxyl- terminal fragments of Renilla luciferase, respectively, was then used to monitor quality and quantity of interacting recombinant-proteins accumulated in the cells. For a proof-of-concept, the method was applied to detect the gibberellin-dependent interaction between GIBBERELLIN INSENSITIVE DWARF1 and SLENDER RICE 1. CONCLUSIONS: A method to detect regulated protein-protein interactions was developed towards establishment of the rice interactome.

Light-dependent expression of flg22-induced defense genes in Arabidopsis.

Chloroplasts have been reported to generate retrograde immune signals that activate defense gene expression in the nucleus. However, the roles of light and photosynthesis in plant immunity remain largely elusive. In this study, we evaluated the effects of light on the expression of defense genes induced by flg22, a peptide derived from bacterial flagellins which acts as a potent elicitor in plants. Whole-transcriptome analysis of flg22-treated Arabidopsis thaliana seedlings under light and dark conditions for 30 min revealed that a number of (30%) genes strongly induced by flg22 (>4.0) require light for their rapid expression, whereas flg22-repressed genes include a significant number of genes that are down-regulated by light. Furthermore, light is responsible for the flg22-induced accumulation of salicylic acid (SA), indicating that light is indispensable for basal defense responses in plants. To elucidate the role of photosynthesis in defense, we further examined flg22-induced defense gene expression in the presence of specific inhibitors of photosynthetic electron transport: 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and 2,5-dibromo-3-methyl-6-isopropyl-benzoquinone (DBMIB). Light-dependent expression of defense genes was largely suppressed by DBMIB, but only partially suppressed by DCMU. These findings suggest that photosynthetic electron flow plays a role in controlling the light-dependent expression of flg22-inducible defense genes.

Chloroplast envelope localization of EDS5, an essential factor for salicylic acid biosynthesis in Arabidopsis thaliana.

Chloroplasts are responsible for biosynthesis of salicylic acid (SA) an important signal molecule in plant immunity. EDS5 is a homolog of the MATE (multidrug and toxic compound extrusion) family of transporters, and is essential for SA biosynthesis. It has been speculated that EDS5 would be involved in the export of SA from chloroplasts. However, the subcellular localization of EDS5 remains largely uncharacterized. We demonstrate here that EDS5 is specifically localized to the chloroplast envelope membrane in Arabidopsis. In addition, we found that EDS5 is preferentially expressed in epidermal cells. These findings suggest that EDS5 is responsible for transport of SA from chloroplasts to the cytoplasm in epidermal cells.

Excess iron inhibits osteoblast metabolism.

Hemochromatosis is an iron overload disorder associated with osteopenia and osteoporosis. To learn more about the effects of iron on bone cells, we examined the effects of ferric ion on the proliferation, differentiation, and mineralization of two types of cultured osteoblasts, the cell line MC3T3-E1 and rat calvarial osteoblast-like (ROB) cells. We used ferric ammonium citrate (FAC) as a donor of ferric ion, and FAC inhibited the proliferation of MC3T3-E1 cells in a dose-dependent manner. FAC (0.1-1 microg/ml) inhibited indices of osteoblast differentiation, such as the expression of type I collagen (mRNA and protein), the activity of alkaline phosphatase, and the deposition of calcium by osteoblasts. These results suggest that iron overload might give rise to osteoporosis by inhibiting osteoblast proliferation and differentiation.