Cytochrome c oxidase subunit I gene in Thalassiosira nordenskioeldii strains inhabiting in cold and warm sea waters.

From the biota beneath the sea ice in Lake Saroma, which is adjacent to Sea of Okhotsk, a diatom culture of Saroma 16 was isolated. Strutted processes and a labiate process in Saroma 16 were characteristic of those in Thalassiosira nordenskioeldii. Similarity search analysis showed that the 826-bp rbcL-3P region sequence of this strain was 100% identical to multiple sequences registered as T. nordenskioeldii in a public database. The 4305-bp PCR-amplified mitochondrial cytochrome c oxidase subunit I (COI) gene (COI)-5P region of Saroma 16 included a 1060-bp open reading frame (ORF), which was interrupted by 934-bp and 2311-bp introns that included frame-shifted ORFs encoding reverse-transcriptase (RTase)-like proteins. Previous reports showed that a strain of the same species, CNS00052, originating from the East China Sea included no introns in the COI, whereas North Atlantic Ocean strains of the same species, such as CCMP992, CCMP993, and CCMP997, included a 2.3-kb intron in the same position as Saroma 16.

Turgor-responsive starch phosphorylation in Oryza sativa stems: A primary event of starch degradation associated with grain-filling ability.

Grain filling ability is mainly affected by the translocation of carbohydrates generated from temporarily stored stem starch in most field crops including rice (Oryza sativa L.). The partitioning of non-structural stem carbohydrates has been recognized as an important trait for raising the yield ceiling, yet we still do not fully understand how carbohydrate partitioning occurs in the stems. In this study, two rice subspecies that exhibit different patterns of non-structural stem carbohydrates partitioning, a japonica-dominant cultivar, Momiroman, and an indica-dominant cultivar, Hokuriku 193, were used as the model system to study the relationship between turgor pressure and metabolic regulation of non-structural stem carbohydrates, by combining the water status measurement with gene expression analysis and a dynamic prefixed 13C tracer analysis using a mass spectrometer. Here, we report a clear varietal difference in turgor-associated starch phosphorylation occurred at the initiation of non-structural carbohydrate partitioning. The data indicated that starch degradation in Hokuriku 193 stems occurred at full-heading, 5 days earlier than in Momiroman, contributing to greater sink filling. Gene expression analysis revealed that expression pattern of the gene encoding α-glucan, water dikinase (GWD1) was similar between two varieties, and the maximum expression level in Hokuriku 193, reached at full heading (4 DAH), was greater than in Momiroman, leading to an earlier increase in a series of amylase-related gene expression in Hokuriku 193. In both varieties, peaks in turgor pressure preceded the increases in GWD1 expression, and changes in GWD1 expression was correlated with turgor pressure. Additionally, a threshold is likely to exist for GWD1 expression to facilitate starch degradation. Taken together, these results raise the possibility that turgor-associated starch phosphorylation in cells is responsible for the metabolism that leads to starch degradation. Because the two cultivars exhibited remarkable varietal differences in the pattern of non-structural carbohydrate partitioning, our findings propose that the observed difference in grain-filling ability originated from turgor-associated regulation of starch phosphorylation in stem parenchyma cells. Further understanding of the molecular mechanism of turgor-regulation may provide a new selection criterion for breaking the yield barriers in crop production.

Isolation and functional characterization of 3-phosphoglycerate dehydrogenase involved in salt responses in sugar beet.

The present study investigated the significance of serine biosynthetic genes for salt stress in sugar beet (Beta vulgaris). We isolated a total of four genes, two each encoding D-3-phosphoglycerate dehydrogenase (BvPGDHa and BvPGDHb) and serine hydroxymethyl transferase (BvSHMTa and BvSHMTb). mRNA transcriptional expression for BvPGDHa was significantly enhanced under salt stress conditions in both leaves and roots of sugar beet, whereas it was reduced for BvPGDHb. On the other hand, BvSHMTa was expressed transiently in leaves and roots under salt stress, whereas expression level of BvSHMTb was not altered. PGDH activity was high in storage root. After salt stress, PGDH activity was increased in leaf, petiole, and root. Recombinant proteins were expressed in Escherichia coli. The K m values for 3-phosphoglycerate in PGDHa and PGDHb were 1.38 and 2.92 mM, respectively. The findings suggest that BvPGDHa and BvSHMTa play an important role during salt stress in sugar beet.

Differential accumulation of glycinebetaine and choline monooxygenase in bladder hairs and lamina leaves of Atriplex gmelini under high salinity.

Atriplex gmelini is a halophyte and possesses bladder hairs on the leaf surface. It is also known to accumulate the osmoprotectant glycinebetaine (GB). However, it remains unclear whether GB and its biosynthetic enzyme choline monooxygenase (CMO) accumulate in the bladder hairs. Microscopic observation of young leaves showed many bladder hairs on their surfaces, but their total number decreased along with leaf maturity. Sodium Green fluorescent approach revealed Na(+) accumulation in bladder cells of young leaves when A. gmelini was grown at high salinity (250 mM NaCl). Due to fewer bladder hairs in mature leaves, Na(+) accumulation was mostly found in mesophyll cells of mature leaves under high salinity. GB accumulation was found at significant level in both bladder- and laminae-cells without any addition of NaCl and its content increased at high salinity. CMO was not found in bladder hairs or young leaf laminae. Instead, the CMO protein expression was observed in mature leaves and that showed increased accumulation with increasing concentration of NaCl. Furthermore, in situ hybridization experiments revealed the expression of a transporter gene for GB, AgBetT, in the bladder hairs. Based on these results, the synthesis and translocation of GB in A. gmelini were discussed.

Rice chalky ring formation caused by temporal reduction in starch biosynthesis during osmotic adjustment under foehn-induced dry wind.

Foehn-like extreme hot and dry wind conditions (34°C, >2.5 kPa vapor pressure deficit, and 7 m s(-1)) strongly affect grain quality in rice (Oryza sativa L.). This is a current concern because of the increasing frequency and intensity of combined heat and water-deficit stress under climate change. Foehn-induced dry wind conditions during the grain-filling stage increase ring-shaped chalkiness as a result of spatiotemporal reduction in starch accumulation in the endosperm, but kernel growth is sometimes maintained by osmotic adjustment. Here, we assess the effects of dry wind on chalky ring formation in environmentally controlled growth chambers. Our results showed that hot and dry wind conditions that lasted for >24 h dramatically increased chalky ring formation. Hot and dry wind conditions temporarily reduced panicle water potential to -0.65 MPa; however, kernel growth was maintained by osmotic adjustment at control levels with increased transport of assimilate to the growing kernels. Dynamic tracer analysis with a nano-electrospray-ionization Orbitrap mass spectrometer and quantitative polymerase chain reaction analysis revealed that starch degradation was negligible in the short-term treatment. Overall expression of starch synthesis-related genes was found to be down-regulated at moderately low water potential. Because the events observed at low water potential preceded the packing of starch granules in cells, we concluded that reduced rates of starch biosynthesis play a central role in the events of cellular metabolism that are altered at osmotic adjustment, which leads to chalky ring formation under short-term hot and dry wind conditions.

Sites of action of elevated CO2 on leaf development in rice: discrimination between the effects of elevated CO2 and nitrogen deficiency.

Elevated CO2 concentrations (eCO2) trigger various plant responses. Despite intensive studies of these responses, the underlying mechanisms remain obscure. In this work, we investigated when and how leaf physiology and anatomy are affected by eCO2 in rice plants. We analyzed the most recently fully expanded leaves that developed successively after transfer of the plant to eCO2. To discriminate between the effects of eCO2 and those of nitrogen deficiency, we used three different levels of N application. We found that a decline in the leaf soluble protein content (on a leaf area basis) at eCO2 was only observed under N deficiency. The length and width of the leaf blade were reduced by both eCO2 and N deficiency, whereas the blade thickness was increased by eCO2 but was not affected by N deficiency. The change in length by eCO2 became detectable in the secondly fully expanded leaf, and those in width and thickness in the thirdly fully expanded leaf, which were at the leaf developmental stages P4 and P3, respectively, at the onset of the eCO2 treatment. The decreased blade length at eCO2 was associated with a decrease in the epidermal cell number on the adaxial side and a reduction in cell length on the abaxial side. The decreased width resulted from decreased numbers of small vascular bundles and epidermal cell files. The increased thickness was ascribed mainly to enhanced development of bundle sheath extensions at the ridges of vascular bundles. These observations enable us to identify the sites of action of eCO2 on rice leaf development.

Development of a variable-wavelength optical rotation detector in the ultraviolet region.

A new type of optical rotation (OR) detector based on the phase retardation of the first-order diffraction beam has been constructed. The proposed detector responded to only OR properties by eliminating the circular dichroism (CD) effect. Thus, it could measure the optical rotatory dispersion curves in the Cotton band. Although the optical system requires the incident beam in which the phase retardation is 0.5π, the actual retardation was estimated to be around 0.3π. It means that the OR signal intensity can be doubled. Since the proposed detector works over a range of UV wavelengths, there was a compound whose OR signal intensity was higher than the CD signal intensity. The OR detection was superior to CD in stability and in defining the baseline.

Expression and substrate specificity of betaine/proline transporters suggest a novel choline transport mechanism in sugar beet.

Proline transporters (ProTs) originally described as highly selective transporters for proline, have been shown to also transport glycinebetaine (betaine). Here we examined and compared the transport properties of Bet/ProTs from betaine accumulating (sugar beet, Amaranthus, and Atriplex,) and non-accumulating (Arabidopsis) plants. Using a yeast mutant deficient for uptake of proline and betaine, it was shown that all these transporters exhibited higher affinity for betaine than proline. The uptake of betaine and proline was pH-dependent and inhibited by the proton uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP). We also investigated choline transport by using a choline transport-deficient yeast mutant. Results revealed that these transporters exhibited a higher affinity for choline uptake rather than betaine. Uptake of choline by sugar beet BvBet/ProT1 was independent of the proton gradient and the inhibition by CCCP was reduced compared with that for uptake of betaine, suggesting different proton binding properties between the transport of choline and betaine. Additionally, in situ hybridization experiments revealed the localization of sugar beet BvBet/ProT1 in phloem and xylem parenchyma cells.