AgarTrap (agar-utilized transformation with pouring solutions) is an easy and efficient Agrobacterium-mediated transformation technique for liverwort Marchantia polymorpha. It is a simplified protocol that can be completed solely on a single solid medium by pouring appropriate solutions. Three main procedures of AgarTrap includes: (1) planting plant tissue for pre-culture, (2) pouring transformation buffer for co-culture with Agrobacterium tumefaciens, (3) pouring selection buffer for selection of transformants. To date, we developed AgarTrap methods by using three tissue types of M. polymorpha namely, sporelings, gemmalings, and mature thallus pieces. Gemmaling is the most effective among all the tested tissue types as its transformation efficiency of the BC3-38 strain is nearly 100%. Our review article includes the protocols of the AgarTrap methods (pp. 93-99).
The cover picture presents a BC3-38 gemmaling transformed by AgarTrap with A. tumefaciens harbouring a binary vector, pMpGWB103-Citrine, that encodes yellow fluorescent protein (Citrine) and hygromycin B phosphotransferase. The AgarTrap was performed by 2 days pre-culture, and 2 days co-culture with A. tumefaciens and sealed by Parafilm under darkness. This picture was taken at 3 days after pouring selection buffer. Red (chlorophyll) and yellow-green (Citrine fluorescence) indicate non-transformed cells and transformed cells, respectively.

This picture is taken by Shoko Tsuboyama using MZ16F stereo fluorescence microscope (Leica Microsystems) and DP73 digital camera (Olympus) at Utsunomiya University (Tochigi, Japan).

Plants synthesize the red/purple pigment anthocyanin upon environmental stimuli such as excess light exposure. An intact leaf of Arabidopsis thaliana exhibits green color, whereas a detached leaf after incubation on water under light illumination for four days accumulates anthocyanin (left). In this issue, Koyama and Sato document that the leaf of the double mutant of class II ETHYLENE RESPONSE FACTOR (ERF) genes decreased the rate and extent of the production of anthocyanin after the incubation under light illumination (right). This mutant also decreased the production of anthocyanin in the strong light condition and, thus, the authors propose the roles of these class II ERFs in the photoinhibition-mediated anthocyanin biosynthesis.

Photographed by Tomotsugu Koyama at Suntory Foundation for Life Sciences in Kyoto, Japan (PowerShot A2300 digital camera, Canon).

For a plant disease to occur, pathogen, plant and environmental conditions must interact. The susceptibility of host plant may change both with developmental stage and time of day. Rice blast caused by Pyricularia oryzae (syn. Magnaporthe oryzae) is a devastating disease of rice. The mechanisms of resistance to P. oryzae have been extensively studied, and the rice-P. oryzae pathosystem has become a model system in plant-microbe interaction studies. However, the mechanisms of resistance to P. oryzae in nonhost remain poorly understood. Yamauchi et al. have used the Arabidopsis-P. oryzae pathosystem to study nonhost resistance (NHR). In this issue, authors (pp. 207–210) reported that NHR to P. oryzae varies with time of inoculation under diurnal conditions in old leaves and old leaves become more susceptible to P. oryzae penetration after inoculation at dusk in pen2-1 plants (lower). These results suggested that leaf age and time of inoculation are involved in NHR to P. oryzae in Arabidopsis.

Photographed by Yuri Yamauchi (Fukui Prefectural University, FPU) in FPU, Japan, 2017 (AxioCam MRc, ZEISS).

GATA4 is a transcription factor that belongs to the GATA family. In this issue Shin et al., reports that the expression of the chimeric repressor for GATA4 (35S:GATA4-SRDX) results in tolerance to nitrogen deficiency in Arabidopsis (pp. 151–158). Roots, which are directly exposed to various environmental conditions in the soil, are important organs that determine plant nutritional balance. Morphological changes in roots can adapt to nutritional availability and increase nutrition uptake efficiency. In particular, an increase in root hair density increases the root surface area and increases the absorption of nutrients and water from the soil. 35S:GATA4-SRDX plants change in root structure and suppress root growth and increase root hair density both under nitrogen sufficient (left upper) and deficient conditions (left lower).

Photograph Location: National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan Photograph Equipment: A fluorescence stereomicroscope (MZ16FA, Leica) equipped with a CCD camera (DFC300FX, Leica)

Powdery mildew is a popular disease caused by ascomycete fungi. As this disease affects near 10,000 plants and causes significant economic loss every year, a development of new tools to combat this disease is of great interest. In this issue, Inada et al. reported that overexpression of the active form of ARA6, a plant-specific member of RAB5 GTPase, impairs powdery mildew proliferation. Powdery mildew fungi form specialized infection hyphae called the haustorium in the apoplast of host epidermal cells. The haustorium is surrounded by the host-derived membrane called the extrahaustorial membrane. Previously, authors reported that host RAB5 GTPases, both plant-specific ARA6 and conventional ARA7, localized to the extrahaustorial membrane. In this issue, authors found that an overexpression of active form of ARA6, but not that of ARA7, suppresses powdery mildew proliferation. These results indicate a specific role of ARA6 in the plant-powdery mildew interaction. In addition, manipulation of the ARA6 activity was suggested to be a possible methodology to overcome this disease.

Photographed by Noriko Inada (Nara Institute of Science and Technology, NAIST) in NAIST, Japan, 2012 (Panasonic DMC-FX30).

Japanese pepper (Zanthoxylum piperitum), “Sansho” in Japanese, is a deciduous shrub, belonging to the family Rutaceae. In Japan, fresh young leaves are sometimes used as garnish and in sauces after mixed with miso (soybean paste) for some Japanese dishes because of its characteristic aroma. The fruits exhibit pungent taste together with strong aroma, and are also utilized as one of the seven components of Japanese blended spices called “Shichimi”. Oil secretory cavities are found at all sinuses of leaves, as shown in this photograph, as well as the surface of fruits and contain high amount of volatile compounds. The grade of Japanese pepper is sometimes determined according to the flavor of high quality of volatile mono- and sesqui-terpenes. In this issue, Fujita et al. have reported the formation of volatile terpenes and their biosynthetic enzymes in secretory cavities of Japanese pepper.

Photographed by Mitsuhiro Aida (Nara Institute of Science and Technology, NAIST) in NAIST, Japan, 2015 (ECLIPSE Ni-U microscope equipped with DIC optics, Nikon; VB-7010 cooled CCD camera, Keyence).

Apple cultivars with homeotic changes, petals to sepals and stamens to carpels, set parthenocarpic fruits. The floral organ changes were caused by destruction of apple MdPISTILLATA (MdPI) gene, which is an orthologue of Arabidopsis class B gene PISTILLATA. The MdPI gene is able to recover the Arabidopsis pi mutant phenotype. The expression of MdPI localized at petals and stamens of apple flowers. The connection between the parthenocarpy and class B mutation was obscure, then transgenic apples suppressed MdPI function was produced. The cover picture represents a flower of antisense MdPI transgenic apple, which was analyzed about parthenocarpy in this article (pp. 395–401).

Location: Division of apple Research (Morioka), NIFTS, NARO Camera: Olympus SP-350

Synecoculture is based on high-density mixed polyculture, which harbors a wide variety of edible plants and rich interactions between environment, flora and fauna: Leaf color change of no-fertilizer cabbage during winter. Tomato in Tokyo can extend its growth until december crawling over chestnut. Cruciferous vegetables (Brassicaceae) easily intercross and produce hybrid varieties with higher yield. Honey bees and butterflies are not only pollinators but also important enhancers of micronutrients profile of crops. Growth in various association of plants augments productivity of community, and enhanced ecological interactions stimulate the expression of health beneficial components such as secondary metabolites. The cooccurrence networks of relevant species from field observation are superimposed.

Location: Synecoculture fields in Ise (Mie), Oiso (Kanagawa) and Todoroki (Tokyo) Camera: Panasonic DMC-LX5, Olympus TG-3

Floral organs are decorated by cuticle with nano-order structure called “nanoridges”, although leaves are covered by plane cuticle. Regulation of cuticle structure and thickness is important for stress tolerance to biotic and abiotic stress, plant growth and petal structural color. In this issue, Oshima and Mitsuda report that the expression of MIXTA-like MYB transcription factors using the promoters of cuticle biosynthesis genes successfully increased accumulation of cuticle in leaves and petals without growth defects in Arabidopsis thaliana (pp. 161–168). Increased nanoridges and ectopic outgrowth of epidermal cell of petal abaxial side, stamen and sepal (from top to bottom rows) in transgenic lines (middle and right columns) compared to those in wild type (left column) affected petal texture.

Photographed by Yoshimi Oshima (National Institute of Advanced Industrial Science and Technology, AIST) in AIST, Japan, 2015 (SEM, KEYENCE VE8800; stereomicroscopic camera, ZEISS AxioCam MRc5)

Strigolactones (SL) are plant hormone that play vital roles in plant architecture. Sugars have been known as important signal molecules to regulate plant growth and development. In this study (pp. 87–97), we found that SL mutants show hyposensitivity to sugar-induced early seedling development arrest. We performed a comparative transcriptomic analysis of max2, hxk1 and wild type (WT) seedlings grown with 2% glucose (G) or mannitol (C) as control. As shown in the figure, several groups of genes show different expression patterns among max2, hxk1 and WT in responses to glucose. These results indicate that SL signal shows crosstalk with sugar signal in HXK1 independent manner.

The transcriptomic data were obtained by short-read sequencing technology (Illumina) combined with a tag-based digital gene expression (DGE) system and analyzed by Pheatmap in R language program.

Switchgrass (Panicum virgatum L.) is an important bioenergy crop. A reliable and efficient transformation method is required to assist with molecular breeding of this crop. After cocultivation with Agrobacterium under optimized conditions, caryopsis-derived Type I (embryogenic and compact) calli formed herbicide-resistant calli (1st row), which showed GFP-fluorescence (2nd row), and then regenerated transgenic shoots (3rd row). The present method was successfully applied to different genotypes, including a major lowland cultivar ‘Alamo’ (left), another lowland cultivar ‘Kanlow’ (middle) and a recalcitrant upland cultivar ‘Trailblazer’ (right) (pp. 19–26).

Photographed by Yoichi Ogawa (Honda Research Institute Japan) at Kazusa Unit (Kisarazu, Japan).

Phosphoenolpyruvate carboxykinase (PEPCK) is known as a key regulatory enzyme in the gluconeogenesis pathway in plants. However, its physiological function in whole plant development is not fully understood in plants with fresh berry-type fruit, including tomato. In this study, in order to obtain more detailed information on the physiological function of PEPCK and the role of gluconeogenesis during development of tomato plant, we generated transgenic tomato plants overexpressing SlPEPCK gene and performed a detailed characterization of those plants. The results indicate multiple roles of PEPCK in the development of the tomato plant, especially in seedling growth, and the effect of the gluconeogenesis pathway on regulation of the sugar and organic acid contents in the fruit.

Photographed by Yong-Xing Huang (University of Tsukuba) in Tsukuba, Japan, 15 and 19 June, 2015.