Kotaro Takayama

Overexpression of a rice heme activator protein gene (OsHAP2E) confers resistance to pathogens, salinity and drought, and increases photosynthesis and tiller number

Heme activator protein (HAP), also known as nuclear factor Y or CCAAT binding factor (HAP/NF-Y/CBF), has important functions in regulating plant growth, development and stress responses. The expression of rice HAP gene (OsHAP2E) was induced by probenazole (PBZ), a chemical inducer of disease resistance. To characterize the gene, the chimeric gene (OsHAP2E::GUS) engineered to carry the structural gene encoding β-glucuronidase (GUS) driven by the promoter from OsHAP2E was introduced into rice. The transgenic lines of OsHAP2Ein::GUS with the intron showed high GUS activity in the wounds and surrounding tissues. When treated by salicylic acid (SA), isonicotinic acid (INA), abscisic acid (ABA) and hydrogen peroxide (H2 O2 ), the lines showed GUS activity exclusively in vascular tissues and mesophyll cells. This activity was enhanced after inoculation with Magnaporthe oryzae or Xanthomonas oryzae pv. oryzae. The OsHAP2E expression level was also induced after inoculation of rice with M. oryzae and X. oryzae pv. oryzae and after treatment with SA, INA, ABA and H2 O2, respectively. We further produced transgenic rice overexpressing OsHAP2E. These lines conferred resistance to M. oryzae or X. oryzae pv. oryzae and to salinity and drought. Furthermore, they showed a higher photosynthetic rate and an increased number of tillers. Microarray analysis showed up-regulation of defence-related genes. These results suggest that this gene could contribute to conferring biotic and abiotic resistances and increasing photosynthesis and tiller numbers.

Early detection of drought stress in tomato plants with chlorophyll fluorescence imaging–practical application of the speaking plant approach in a greenhouse–

Abstract The chlorophyll fluorescence imaging technique is useful for evaluating photosynthetic functions of plants without actually touching the plant. In our previous study, we developed a chlorophyll fluorescence imaging system for tomato plants cultivated in greenhouses. This imaging system measures the chlorophyll fluorescence induction phenomenon, a dynamic change in chlorophyll fluorescence intensity induced by illuminating a dark-adapted leaf with a stable intensity excitation light, and analyzes the shape of the induction curve, i.e., the temporal course of chlorophyll fluorescence intensity during this phenomenon. The shape of the induction curve is characterized by an initial maximum peak (P), subsequent transient dip (S), and secondary small peak (M). We defined an index, the photosynthetic function index (PFI; fluorescence intensity of P divided by the average fluorescence intensity from S to M), to evaluate the shape of the induction curve. In this study, we applied this system to detect drought stress in tomato plants cultivated in a semi-commercial greenhouse. PFI was clearly lower in stressed plants than in healthy plants. The decreased PFI in stressed plants is probably attributable to photosynthetic dysfunction in these plants.

Image Instrumentation of Chlorophyll a Fluorescence for Diagnosing Photosynthetic Injury

Environmental stress factors such as air pollutants, agricultural chemicals, water deficit, chilling, and UV light can affect the health of plants (Larcher 1995; Kramer and Boyer 1995; Yunus and Iqbal 1996; De Kok and Stulen 1998). The first symptoms to appear are decreases in photosynthesis and growth. Later symptoms include visible injury of leaves and withering. In recent years forest decline, which may be due to environmental stress factors including meteorological changes, has been widely reported (Schulze et al. 1989; Larcher 1995; Sandermann et al. 1997).

Evapotranspiration Estimate by Heat Balance Equation

A simple heat balance equation for the plant canopy model from which the Penman- Monteith equation was derived is used to estimate evapotranspiration from a plant canopy. Incoming radiation downward and upward, air temperature and wind speed above the canopy are the only four factors to be measured. Estimated evapotranspiration is in good agreement with the values measured by an accurate scale in wet and dry conditions. This method was proven to be simpler and more accurate than that based on the Penman-Monteith equation.

Transcriptome Analysis of Plant Hormone-Related Tomato (Solanum lycopersicum) Genes in a Sunlight-Type Plant Factory.

In plant factories, measurements of plant conditions are necessary at an early stage of growth to predict harvest times of high value-added crops. Moreover, harvest qualities depend largely on environmental stresses that elicit plant hormone responses. However, the complexities of plant hormone networks have not been characterized under nonstress conditions. In the present study, we determined temporal expression profiles of all genes and then focused on plant hormone pathways using RNA-Seq analyses of gene expression in tomato leaves every 2 h for 48 h. In these experiments, temporally expressed genes were found in the hormone synthesis pathways for salicylic acid, abscisic acid, ethylene, and jasmonic acid. The timing of CAB expression 1 (TOC1) and abscisic acid insensitive 1 (ABA1) and open stomata 1 (OST1) control gating stomata. In this study, compare with tomato and Arabidopsis thaliana, expression patterns of TOC1 have similarity. In contrast, expression patterns of tomato ABI1 and OST1 had expression peak at different time. These findings suggest that the regulation of gating stomata does not depend predominantly on TOC1 and significantly reflects the extracellular environment. The present data provide new insights into relationships between temporally expressed plant hormone-related genes and clock genes under normal sunlight conditions.

Integrating Transient Heterogeneity of Non-Photochemical Quenching in Shade-Grown Heterobaric Leaves of Avocado (Persea americana L.): Responses to CO2 Concentration, Stomatal Occlusion, Dehydration and Relative Humidity

Long-lived shade leaves of avocado had extremely low rates of photosynthesis. Gas exchange measurements of photosynthesis were of limited use, so we resorted to Chl fluorescence imaging (CFI) and spot measurements to evaluate photosynthetic electron transport rates (ETRs) and non-photochemical quenching (NPQ). Imaging revealed a remarkable transient heterogeneity of NPQ during photosynthetic induction in these hypostomatous, heterobaric leaves, but was adequately integrated by spot measurements, despite long-lasting artifacts from repeated saturating flashes during assays. Major veins (mid-vein, first- and second-order veins) defined areas of more static large-scale heterogeneous NPQ, with more dynamic small-scale heterogeneity most strongly expressed in mesophyll cells between third- and fourth-order veins. Both responded to external CO2 concentration ([CO2]), occlusion of stomata with Vaseline™, leaf dehydration and relative humidity (RH). We interpreted these responses in terms of independent behavior of stomata in adjacent areoles that was largely expressed through CO2-limited photosynthesis. Heterogeneity was most pronounced and prolonged in the absence of net CO2 fixation in 100 p.p.m. [CO2] when respiratory and photorespiratory CO2 cycling constrained the inferred ETR to ~75% of values in 400 or 700 p.p.m. [CO2]. Likewise, sustained higher NPQ under Vaseline™, after dehydration or at low RH, also restricted ETR to ~75% of control values. Low NPQ in chloroplast-containing cells adjacent to major veins but remote from stomata suggested internal sources of high [CO2] in these tissues.

Detection of Diurnal Variation of Tomato Transcriptome through the Molecular Timetable Method in a Sunlight-Type Plant Factory

The timing of measurement during plant growth is important because many genes are expressed periodically and orchestrate physiological events. Their periodicity is generated by environmental fluctuations as external factors and the circadian clock as the internal factor. The circadian clock orchestrates physiological events such as photosynthesis or flowering and it enables enhanced growth and herbivory resistance. These characteristics have possible applications for agriculture. In this study, we demonstrated the diurnal variation of the transcriptome in tomato (Solanum lycopersicum) leaves through molecular timetable method in a sunlight-type plant factory. Molecular timetable methods have been developed to detect periodic genes and estimate individual internal body time from these expression profiles in mammals. We sampled tomato leaves every 2 h for 2 days and acquired time-course transcriptome data by RNA-Seq. Many genes were expressed periodically and these expressions were stable across the 1st and 2nd days of measurement. We selected 143 time-indicating genes whose expression indicated periodically, and estimated internal time in the plant from these expression profiles. The estimated internal time was generally the same as the external environment time; however, there was a difference of more than 1 h between the two for some sampling points. Furthermore, the stress-responsive genes also showed weakly periodic expression, implying that they were usually expressed periodically, regulated by light–dark cycles as an external factor or the circadian clock as the internal factor, and could be particularly expressed when the plant experiences some specific stress under agricultural situations. This study suggests that circadian clock mediate the optimization for fluctuating environments in the field and it has possibilities to enhance resistibility to stress and floral induction by controlling circadian clock through light supplement and temperature control.

Evaluation of Tomato Fruit Color Change with Different Maturity Stages and Storage Temperatures Using Image Analysis

Abstract The effects of storage duration and temperature on the tomato fruit color change and quality with different maturity stages tomato were investigated in this study. Tomatoes were grown hydroponically in high technology greenhouse. Tomato fruit samples with green to red were stored in cool incubator for 48 h. The storage temperature was adjusted at 15 °C and 20 °C. The maturity stage of tomato fruit was evaluated with chiromaticity by image analysis. Little tomato fruit color change with storage was observed in large maturity stage (red fruit) regardless of storage temperature. Chromaticity in small maturity stage (green fruit) was increased with storage time. The sugar content of fruit was increased and fruit firmness was decreased with storage at both temperatures for 15 °C and 20 °C regardless of maturity stage.

Imaging Heterogeneity of Xanthophyll-Independent Non-photochemical Quenching During Photosynthetic Induction in Shade-Grown Leaves of Avocado (Persea americana L.)

Leaves Of Shade-Grown Avocado Plants Rich In Lutein Epoxide (Lx) Were Used To Image Heterogeneity In Chlorophyll Fluorescence Quenching And To Measure Co2 Uptake And Stomatal Conductance During Photosynthetic Induction For 20 Min After Transition From Dark To Light, And After Changes Between 100, 400 And 700 Ppm Co2 At Growth Irradiance. We Found That Non-Photochemical Quenching (Npq) Was Initially Heterogeneous, With Marked Differences Between Cells In Tissues Defined By Minor Veins And Those Adjacent To Primary And Secondary Veins. The Duration And Extent Heterogeneity Of Transients In Npq, Photosynthetic Rate And Stomatal Conductance Were Sensitive To Co2 Concentration, Whereas Psii Efficiency (ΦPsii,) Was Not. There Were No Changes In The De-Epoxidation Status Of Xanthophylls Pigments In Equivalent Treatments, Implying That The Dynamic, Heterogeneous, Stomatally-Dependent And Co2-Responsive Npq May Involve Quenching Processes That Occur In Reaction Centres Prior To Stabilization Of Heat Dissipation In The Antennae.

Development of a Multi-Operation System for Intelligent Greenhouses

Abstract To resolve the problem of declination of Japanese agriculture, plant factories with automation, quality control, robotization and speaking plant approach are necessary. The multi operation system described in this paper has running unit with automatic position sensing. Growth environment measurement unit has transpiration, photosynthesis, distance and temperature sensors to obtain plant growth information. The pest control unit uses the antiseptic effect of ozone water. The harvesting unit is used for cucumbers that grow fast; recognition of cucumbers ready to be harvested is achieved through distance information gathered by an attached photo interrupter and distance sensors. The development of multi-operation robot is continued by developing controlling program that can change the operating pattern by sharing the contents by each controlling and operating unit.