Tamyb10-D1 restores red grain color and increases grain dormancy via suppressing expression of TaLTP2.128, non-specific lipid transfer protein in wheat

Grain dormancy of wheat is closely associated with grain color: red-grained lines show higher dormancy than white-grained lines. The production of red pigments is regulated by R-1, Tamyb10 gene. However, the relation between grain color and dormancy remains unknown. For this study, we generated transgenic lines which were introduced a DNA fragment containing Tamyb10-D1 gene and its a 2 kb promoter including the 5′ untranslated region into white-grained wheat. Transgenic lines showed red-grained and higher dormant traits. Contents of plant hormones and gene expression of embryos at 30 days after pollination were examined in a wild type and a transgenic line. No differences were observed in the contents of plant hormones, but several genes are differentially expressed between these lines. One differentially expressed gene, TaLTP2.128, is a member of non-specific lipid transfer proteins. It was expressed higher in white grains than in red grains. A putative amino acid sequence showed similarity to that of OsHyPRP5, which is identified as QTL controlling low-temperature germinability in rice. Expression of TaLTP2.128 was increased by grain imbibition. The increasing levels were higher not only in other white-grained lines, but also in non-dormant red-grained lines. TaLTP2.128 was expressed at a quite early stage of germination. These study findings indicate that Tamyb10 regulates dormancy release by the modification of TaLTP2.128 acting as trigger of germination

Life-Course Monitoring of Endogenous Phytohormone Levels under Field Conditions Reveals Diversity of Physiological States among Barley Accessions

Agronomically important traits often develop during the later stages of crop growth as consequences of various plant–environment interactions. Therefore, the temporal physiological states that change and accumulate during the crop’s life course can significantly affect the eventual phenotypic differences in agronomic traits among crop varieties. Thus, to improve productivity, it is important to elucidate the associations between temporal physiological responses during the growth of different crop varieties and their agronomic traits. However, data representing the dynamics and diversity of physiological states in plants grown under field conditions are sparse. In this study, we quantified the endogenous levels of five phytohormones — auxin, cytokinins (CKs), ABA, jasmonate and salicylic acid — in the leaves of eight diverse barley (Hordeum vulgare) accessions grown under field conditions sampled weekly over their life course to assess the ongoing fluctuations in hormone levels in the different accessions under field growth conditions. Notably, we observed enormous changes over time in the development-related plant hormones, such as auxin and CKs. Using 3′ RNA-seq-based transcriptome data from the same samples, we investigated the expression of barley genes orthologous to known hormone-related genes of Arabidopsis throughout the life course. These data illustrated the dynamics and diversity of the physiological states of these field-grown barley accessions. Together, our findings provide new insights into plant–environment interactions, highlighting that there is cultivar diversity in physiological responses during growth under field conditions

Proteasome-associated ubiquitin ligase relays target plant hormone-specific transcriptional activators

The ubiquitin-proteasome system is vital to hormone-mediated developmental and stress responses in plants. Ubiquitin ligases target hormone-specific transcriptional activators (TAs) for degradation, but how TAs are processed by proteasomes remains unknown. We report that in Arabidopsis, the salicylic acid– and ethylene-responsive TAs, NPR1 and EIN3, are relayed from pathway-specific ubiquitin ligases to proteasome-associated HECT-type UPL3/4 ligases. Activity and stability of NPR1 were regulated by sequential action of three ubiquitin ligases, including UPL3/4, while proteasome processing of EIN3 required physical handover between ethylene-responsive SCF(EBF2) and UPL3/4 ligases. Consequently, UPL3/4 controlled extensive hormone-induced developmental and stress-responsive transcriptional programs. Thus, our findings identify unknown ubiquitin ligase relays that terminate with proteasome-associated HECT-type ligases, which may be a universal mechanism for processive degradation of proteasome-targeted TAs and other substrates

The mechanism of SO2 -induced stomatal closure differs from O3 and CO2 responses and is mediated by nonapoptotic cell death in guard cells.

Plants closing stomata in the presence of harmful gases is believed to be a stress avoidance mechanism. SO2 , one of the major airborne pollutants, has long been reported to induce stomatal closure, yet the mechanism remains unknown. Little is known about the stomatal response to airborne pollutants besides O3 . SLOW ANION CHANNEL-ASSOCIATED 1 (SLAC1) and OPEN STOMATA 1 (OST1) were identified as genes mediating O3 -induced closure. SLAC1 and OST1 are also known to mediate stomatal closure in response to CO2 , together with RESPIRATORY BURST OXIDASE HOMOLOGs (RBOHs). The overlaying roles of these genes in response to O3 and CO2 suggested that plants share their molecular regulators for airborne stimuli. Here, we investigated and compared stomatal closure event induced by a wide concentration range of SO2 in Arabidopsis through molecular genetic approaches. O3 - and CO2 -insensitive stomata mutants did not show significant differences from the wild type in stomatal sensitivity, guard cell viability, and chlorophyll content revealing that SO2 -induced closure is not regulated by the same molecular mechanisms as for O3 and CO2 . Nonapoptotic cell death is shown as the reason for SO2 -induced closure, which proposed the closure as a physicochemical process resulted from SO2 distress, instead of a biological protection mechanism

BdWRKY38 is required for the incompatible interaction of Brachypodium distachyon with the necrotrophic fungus Rhizoctonia solani

Rhizoctonia solani is a soil‐borne necrotrophic fungus that causes sheath blight in grasses. The basal resistance of compatible interactions between R. solani and rice is known to be modulated by some WRKY transcription factors (TFs). However, genes and defense responses involved in incompatible interaction with R. solani remain unexplored, because no such interactions are known in any host plants. Recently, we demonstrated that Bd3‐1, an accession of the model grass Brachypodium distachyon, is resistant to R. solani and, upon inoculation with the fungus, undergoes rapid induction of genes responsive to the phytohormone salicylic acid (SA) that encode the WRKY TFs BdWRKY38 and BdWRKY44. Here, we show that endogenous SA and these WRKY TFs positively regulate this accession‐specific R. solani resistance. In contrast to a susceptible accession (Bd21), the infection process in the resistant accessions Bd3‐1 and Tek‐3 was suppressed at early stages before the development of fungal biomass and infection machinery. A comparative transcriptome analysis during pathogen infection revealed that putative WRKY‐dependent defense genes were induced faster in the resistant accessions than in Bd21. A gene regulatory network (GRN) analysis based on the transcriptome dataset demonstrated that BdWRKY38 was a GRN hub connected to many target genes specifically in resistant accessions, whereas BdWRKY44 was shared in the GRNs of all three accessions. Moreover, overexpression of BdWRKY38 increased R. solani resistance in Bd21. Our findings demonstrate that these resistant accessions can activate an incompatible host response to R. solani, and BdWRKY38 regulates this response by mediating SA signaling

Low temperature modulates natural peel degreening in lemon fruit independently of endogenous ethylene

Peel degreening is an important aspect of fruit ripening in many citrus fruit, and previous studies have shown that it can be advanced by ethylene treatment or by low-temperature storage. However, the important regulators and pathways involved in natural peel degreening remain largely unknown. To determine how natural peel degreening is regulated in lemon fruit (Citrus limon), we studied transcriptome and physiochemical changes in the flavedo in response to ethylene treatment and low temperatures. Treatment with ethylene induced rapid peel degreening, which was strongly inhibited by the ethylene antagonist, 1-methylcyclopropene (1-MCP). Compared with 25 degrees C, moderately low storage temperatures of 5-20 degrees C also triggered peel degreening. Surprisingly, repeated 1-MCP treatments failed to inhibit the peel degreening induced by low temperature. Transcriptome analysis revealed that low temperature and ethylene independently regulated genes associated with chlorophyll degradation, carotenoid metabolism, photosystem proteins, phytohormone biosynthesis and signalling, and transcription factors. Peel degreening of fruit on trees occurred in association with drops in ambient temperature, and it coincided with the differential expression of low temperature-regulated genes. In contrast, genes that were uniquely regulated by ethylene showed no significant expression changes during on-tree peel degreening. Based on these findings, we hypothesize that low temperature plays a prominent role in regulating natural peel degreening independently of ethylene in citrus fruit

Mechanosensory trichome cells evoke a mechanical stimuli–induced immune response in Arabidopsis thaliana

Perception of pathogen-derived ligands by corresponding host receptors is a pivotal strategy in eukaryotic innate immunity. In plants, this is complemented by circadian anticipation of infection timing, promoting basal resistance even in the absence of pathogen threat. Here, we report that trichomes, hair-like structures on the epidermis, directly sense external mechanical forces, including raindrops, to anticipate pathogen infections in Arabidopsis thaliana. Exposure of leaf surfaces to mechanical stimuli initiates the concentric propagation of intercellular calcium waves away from trichomes to induce defence-related genes. Propagating calcium waves enable effective immunity against pathogenic microbes through the CALMODULIN-BINDING TRANSCRIPTION ACTIVATOR 3 (CAMTA3) and mitogen-activated protein kinases. We propose an early layer of plant immunity in which trichomes function as mechanosensory cells that detect potential risks

蔬菜水耕栽培の実用化に関する研究 XVII : 定植時の葉数がトマトの生育・収量におよぼす影響(農学部門)

トマトの水耕栽培における定植の適期を決定するために, 春作と秋作とにつき, 展開葉数が3,6,9,12枚時に定植して生育, 収量を比較した。品種は大型福寿, 培養液はれき耕用園試処方第1例の50%液を使用した。定植がおそくなると, 定植時および栽培終了時の草丈が大, 葉の大きさが小, 栽培終了時の植物体乾物含有率が大, 栽培前半の養水分吸収量が少, 開花数が少, 開花日がおそく, 開花より果実収穫までの日数が少となった。収量は, 春作では定植の早い区で大となったが, 秋作では定植のおそい区で大となった。Ohgata-Fukujyu tomatoes sown in sand and then water-cultured in nursery bed, were planted out in the culture bed at 3-, 6-, 9-, or 12-leaf stage, to determine the adequate age of transplants at planting out, in water culture. As the results of the later planting out, plant heights both at the time of planting out and the termination of experiment were higher, leaves were smaller, dry matter contents of plant component organs were higher, water and nutrient absorptions during early growth were lower, no. of flowers was less and no. of days required for fruit maturation was less, than those by the early planting out. The yield was lower and was often delayed by the later planting out in the spring crop, while it was higher and was delayed by a few days by the later planting out in the fall crop

Phytohormones in red seaweeds: a technical review of methods for analysis and a consideration of genomic data

Emerging studies suggest that seaweeds contain phytohormones; however, their chemical entities, biosynthetic pathways, signal transduction mechanisms, and physiological roles are poorly understood. Until recently, it was difficult to conduct comprehensive analysis of phytohormones in seaweeds because of the interfering effects of cellular constituents on fine quantification. In this review, we discuss the details of the latest method allowing simultaneous profiling of multiple phytohormones in red seaweeds, while avoiding the effects of cellular factors. Recent studies have confirmed the presence of indole-3-acetic acid (IAA), N6-(Δ2-isopentenyl)adenine(iP), (+)-abscisic acid (ABA), and salicylic acid, but not of gibberellins and jasmonate, in Pyropia yezoensis and Bangia fuscopurpurea. In addition, an in silico genome-wide homology search indicated that red seaweeds synthesize iP and ABA via pathways similar to those in terrestrial plants, although genes homologous to those involved in IAA biosynthesis in terrestrial plants were not found, suggesting the epiphytic origin of IAA. It is noteworthy that these seaweeds also lack homologues of known factors involved in the perception and signal transduction of IAA, iP, and ABA. Thus, the modes of action of these phytohormones in red seaweeds are unexpectedly dissimilar to those in terrestrial plants