Leaf senescence is controlled developmentally and environmentally and is affected by numerous genes, including transcription factors. An Arabidopsis NAC domain transcription factor, ATAF2, is known to regulate biotic stress responses. Recently, we have demonstrated that ATAF2 upregulates ORE1, a key regulator of leaf senescence. Here, to investigate the function of ATAF2 in leaf senescence further, we generated and analyzed overexpressing transgenic and T‐DNA inserted mutant lines. Transient expression analysis indicated that ATAF2 upregulates several NAC domain transcription factors that regulate senescence. Indeed, ATAF2 overexpression induced the expression of senescence‐related genes, thereby accelerating leaf senescence, whereas the expression of such genes in ataf2 mutants was lower than that of wild‐type plants. Furthermore, the ataf2 mutants exhibited significant delays in dark‐induced leaf senescence. It was also found that ATAF2 induces the expression of transcription factors, which both promotes and represses leaf senescence. The present study demonstrates that ATAF2 promotes leaf senescence in response to developmental and environmental signals.

Readily available moisture in the root zone is very important for optimum plant growth. The available techniques to determine soil moisture content have practical limitations owing to their high cost, dependence on labor, and time consumption. We have developed a prototype for automated soil moisture monitoring using a low-cost capacitive soil moisture sensor (SKU:SEN0193) for data acquisition, connected to the internet. A soil-specific calibration was performed to integrate the sensor with the automated soil moisture monitoring system. The accuracy of the soil moisture measurements was compared with those of a gravimetric method and a well-established soil moisture sensor (SM-200, Delta-T Devices Ltd, Cambridge, UK). The root-mean-square error (RMSE) of the soil water contents obtained with the SKU:SEN0193 sensor function, the SM-200 manufacturer’s function, and the SM-200 soil-specific calibration function were 0.09, 0.07, and 0.06 cm3 cm−3, for samples in the dry to saturated range, and 0.05, 0.08, and 0.03 cm3 cm−3, for samples in the field capacity range. The repeatability of the measurements recorded with the developed calibration function support the potential use of the SKU:SEN0193 sensor to minimize the risk of soil moisture stress or excess water application.

The ARABIDOPSIS THALIANA ACTIVATION FACTOR 2 (ATAF2) protein has been demonstrated to be involved in various biological processes including biotic stress responses, photo morphogenesis, and auxin catabolism. However, the transcriptional function of ATAF2 currently remains elusive. Therefore, to further understand the molecular function of ATAF2, we evaluated the transcriptional activities of ATAF2 using a transient assay system in this study. We used an effector consisting of a GAL4-DNA binding domain (GAL4-BD) fused to ATAF2, and observed upregulated reporter gene expression, suggesting that ATAF2 potentially has transcriptional activation activity. ATAF2 has been shown to activate reporter gene expression under the control of the ORE1 promoter. By contrast, ATAF2 significantly repressed reporter gene expression driven by the NIT2 promoter. These data suggest that ATAF2 is a bifunctional transcription factor that can alter target gene expression depending on the promoter sequences.

The Arabidopsis thaliana NAM, ATAF1/2 and CUC2 (NAC) domain transcription factor VND-INTERACTING1 (VNI1) was previously isolated as an interacting factor of VASCULAR-RELATED NAC-DOMAIN PROTEIN7 (VND7), a key regulator of xylem vessel differentiation, in a yeast two-hybrid screening. Here, we characterized VNI1 and its closest homolog, ANAC103, at the molecular level. Both VNI1 and ANAC103 interacted in vitro not only with VND proteins but also with other NAC domain proteins, such as NAC1 and CUC2. A transient expression assay showed that both VNI1 and ANAC103 are transcriptional activators. ANAC103 promoter activity was detected in vascular tissues, as well as in the trichomes, guard cells, and margins of young leaves. These data suggest that VNI1 and ANAC103 promote the differentiation of various types of cells by modulating the transcriptional activities of a wide range of NAC domain transcription factors.

A NAC domain transcription factor, VND-INTERACTING2 (VNI2) is originally isolated as an interacting protein with another NAC domain transcription factor, VASCULAR-RELATED NAC-DOMAIN7 (VND7), a master regulator of xylem vessel element differentiation. VND7 directly or indirectly induces expression of a number of genes associated with xylem vessel element differentiation, while VNI2 inhibits the transcriptional activation activities of VND7 by forming a protein complex. VNI2 is expressed at an earlier stage of xylem vessel element differentiation than VND7.Here, to investigate whether VND7 also affects VNI2, a transient expression assay was performed. We demonstrated that VND7 downregulated VNI2 expression. Other transcription factors involved in xylem vessel formation did not show the negative regulation of VNI2 expression. Rather, MYB83, a downstream target of VND7, upregulated VNI2 expression. By using the deletion series of the VNI2 promoter, a 400 bp region was identified as being responsible for downregulation by VND7. These data suggested that VND7 and VNI2 mutually regulate each other, and VNI2 expression is both positively and negatively regulated in the transcriptional cascade.

Systems that are made of several low-cost gas sensors with automatic gas sampling may have the potential to serve as reliable fast methane analyzers. However, there is a lack of reports about such types of systems evaluated under field conditions. Here, we developed a continuous methane monitoring system with automated gas sampling unit using low-cost gas sensors, TGS 2611 and MQ-4, that use a simple cloud-based data acquisition platform. We verified the consistency, repeatability, and reproducibility of the data obtained by TGS 2611 and MQ-4 low-cost gas sensors by measuring high- and low-concentration methane samples. The normalized root-mean-square errors (NRMSEs) of the samples with high methane concentrations, [CH4] of 3, 4, 6, and 7%, were 0.0788, 0.0696, 0.1198, and 0.0719 for the TGS 2611 sensor, respectively, and were confirmed using a gas chromatograph as a reference analyzer. The NRMSEs of the samples with low [CH4] of 0.096, 0.145, 0.193, and 0.241% measured by the TGS 2611 sensor were 0.0641, 0.1749, 0.0157, and 0.1613, whereas those NRMSEs of the same concentrations measured by the MQ-4 sensor were 0.3143, 0.5766, 0.6301, and 0.6859, respectively. Laboratory-scale anaerobic digesters were tested using the developed system. The anaerobic digesters were continuously operated for 2 months, demonstrating the potential use of sensors for detecting and monitoring methane in the field level application. This study utilized a unique way to combine the advantages of low-cost sensors and develop a reliable monitoring system by minimizing drawbacks of low-cost sensors.

An Arabidopsis NAC domain transcription factor VND-INTERACTING2 (VNI2) was originally isolated as an interacting protein with another NAC domain transcription factor, VASCULAR-RELATED NAC-DOMAIN7 (VND7), a master regulator of xylem vessel element differentiation. VNI2 inhibits transcriptional activation activity of VND7 by forming a protein complex. Here, to obtain insights into how VNI2 regulates VND7, we tried to identify the amino acid region of VNI2 required for inhibition of VND7. VNI2 has an amino acid sequence similar to the ETHYLENE-RESPONSIVE ELEMENT BINDING FACTOR (ERF)-associated amphiphilic repression (EAR) motif, conserved in transcriptional repressors, at the C-terminus. A transient expression assay showed that the EAR-like motif of VNI2 was not required for inhibition of VND7. The C-terminal deletion series of VNI2 revealed that 10 amino acid residues, highly conserved in the VNI2 orthologs contributed to effective repression of the transcriptional activation activity of VND7. Observation of transgenic plants ectopically expressing VNI2 showed that the identified 10 amino acid sequence strongly affected xylem vessel formation and plant growth. These data indicated that the 10 amino acid sequence of VNI2 has an important role in its transcriptional repression activity and negative regulation of xylem vessel formation.

Communication technologies are moving toward higher microwave frequencies and bandwidths to satisfy the growing demand for high data rates. The concern about the possible effects of microwaves on plants and animals has increased recently. There is still uncertainty concerning the effects of microwaves on plants. The present study was conducted to investigate the effect of industrial, scientific and medical (ISM) radio band microwaves on seedlings and seeds of Arabidopsis thaliana (L.). In vitro growing A. thaliana wild-type seedlings and seeds were exposed to 2.45 GHz continuous-wave microwaves at a power flux density of 1.0 ± 0.1 W m −2 for 48 h. Microwave exposure increased the hydrogen peroxide content, photosynthetic pigments, nonphotochemical quenching and fluorescence of the seedlings, while peroxidase activity and F v /F m values were unchanged. Anthocyanin and malondialdehyde were decreased. Seed germination rate, fresh weight and photosynthetic pigment contents of 10-day-old seedlings obtained from microwaves exposed seeds remained unchanged. Results confirmed the inexistence of oxidative stress but a stimulatory effect of microwave on A. thaliana seedlings. The increased hydrogen peroxide content and nonphotochemical quenching suggest acceptance of extra photon energy and a portion of the excess captured photon passing through the photosystem, while a portion of energy dissipated as heat.