Intermediate perennial-annual populations ofOryza perennis found in Thailand and their evolutionary significance

To reexamine the mode of variations in adaptive mechanisms in the Asian form ofOryza perennis, the breeding behavior of natural populations was observed at eight sites selected in Thailand. One population consisted of seedlings only (annual), and five consisted of ratooned plants only (perennial), while two others were mixtures of both. The annual population had a larger number of buried seeds at the habitat than had the others. In the habitat of the annual population, annual species were predominant, while perennial populations tended to coexist with perennial species. The annual population was in a temporary swamp, while perennial populations were found at sites more deeply inundated in the rainy season and retaining moisture in the dry season. This indicated the role of water stress in conditioning the reproductive strategy. Observations of character variations among plants from those populations in a uniform condition proved that the seedling population was of an annual type while those performing mixed sexual and asexual propagations were of an intermediate perennial-annual type. Isoenzymic variations controlled by alleles at two known loci indicated that the two intermediate populations were highly polymorphic and heterozygous. One of them consisted of nine separate clumps which differed in their characteristics. On the basis of these observations, the dynamics of differentiation of this species in adaptive strategy is discussed. It is further suggested that the intermediate perennial-annual type is probably the wild progenitor ofO. sativa. Contribution from National Institute of Genetics, Japan, No. 1308. Partly presented by H.I. Oka at a Symposium, “Problems in evolutionary and population genetics”, XIV International Congress of Genetics, Moscow, August 1978.     

Location of a ColE1 deoxyribonucleic acid region that affects the plaque-forming ability of lambda-ColE1 hybrid bacteriophage.

The plaque-forming ability of a hybrid phage between plasmidColE1 and phage lambda carrying amber mutations in genes O and P was inhibited by the presence of ColE1 in suppressor-deficient Escherichia coli cells. ColE1 deoxyribonucleic acid regions concerned with this inhibition were examined by using various deletion and transposon insertion derivatives of ColE1, and it was found that the presence of the deoxyribonucleic acid region extending between 420 and 613 base pairs upstream from the initiation site of ColE1 deoxyribonucleic acid replication (J. Tomizawa, H. Ohmori, and R. E. Bird, Proc. Natl. Acad. Sci. U. S. A. 74: 1865--1869, 1977) was essential for this function.     

Tank cultivation of <Emphasis Type="Italic">Ulva prolifera</Emphasis> in deep seawater using a new “germling cluster” method

A new “germling cluster” method is proposed for tank cultivation of seaweed in a free-floating form. This method was applied to the tank cultivation of Ulva prolifera using deep seawater (DSW) pumped up from over 300 m depth off the cape of Muroto in southwest Japan. Numerous zoids of U. prolifera were induced by cutting thalli into 1–2 mm long pieces. Three days after fragment production, the zoids were released. The zoid suspension was concentrated to a density of more than 10⁴ zoids per mL medium, and placed in a Petri dish for culture. The dense, germinating zoids began to adhere to each other and form aggregations. The germling aggregations were then removed from the bottom of the dish and torn into a large number of small “germling clusters” using an electric mixer. Each cluster contained 10–100 germlings. Once the germling clusters had attained more than 5 mm diameter in culture, they were transplanted as free-floating forms to a 500 L outdoor tank with continuous aeration, to which DSW was supplied at an exchange rate of 3 volumes per day. As a result, the average daily growth rate (DGR) in the tank throughout the year was 37%, though the DGR fluctuated with seasonal temperature changes.     

Spike‐dependent calcium influx in dendrites of the cricket giant interneuron

Identified wind‐sensitive giant interneurons in the cricket's cercal sensory system integrate cercal afferent signals and release an avoidance behavior. A calcium‐imaging technique was applied to the giant interneurons to examine the presence of the voltage‐dependent Ca²⁺ channels (VDCCs) in their dendrites. We found that presynaptic stimuli to the cercal sensory nerve cords elevated the cytosolic Ca²⁺ concentration ([Ca²⁺]_i) in the dendrites of the giant interneurons. The dendritic Ca²⁺ rise coincided with the spike burst of the giant interneurons, and the rate of Ca²⁺ rise depended on the frequency of the action potentials. These results suggest that the action potentials directly caused [Ca²⁺]_i increase. Observation of the [Ca²⁺]_i elevation induced by depolarizing current injection demonstrates the presence of the VDCCs in the dendrites. Although hyperpolarizing current injection into the giant interneuron suppressed action potential generation, EPSPs could induce no [Ca²⁺]_i increase. This result means that ligand‐gated channels do not contribute to the synaptically stimulated Ca²⁺ elevation. On the other hand, antidromically stimulated spikes also increased [Ca²⁺]_i in all cellular regions including the dendrites. And bath application of a mixture of Ni²⁺, Co²⁺, and Cd²⁺ or tetrodotoxin inhibited the [Ca²⁺]_i elevation induced by the antidromic stimulation. From these findings, we suppose that the axonal spikes antidromically propagate and induce the Ca²⁺ influx via VDCCs in the dendrites. The spike‐dependent Ca²⁺ elevation may regulate the sensory signals processing via second‐messenger cascades in the giant interneurons. © 2000 John Wiley & Sons, Inc. J Neurobiol 44: 45–56, 2000     

Dual regulation of sphingosine 1-phosphate-induced phospholipase D activity through RhoA and protein kinase C-alpha in C2C12 myoblasts

Previous studies showed that in C2C12 cells, phospholipase D (PLD) and its known regulators, RhoA and protein kinase Calpha (PKCalpha), were downstream effectors in sphingosine 1-phosphate (SPP) signalling. Moreover, the role of PKC for SPP-mediated PLD activation and the requirement of PKCalpha for RhoA translocation were reported. The present results demonstrated that inactivation of RhoA, by overexpression of RhoGDP dissociation inhibitor (RhoGDI) as well as treatment with C3 exotoxin, attenuated SPP-stimulated PLD activity, supporting the involvement of RhoA in the stimulation of PLD activity by the bioactive lipid in C2C12 myoblasts. In addition, the effect of PKCalpha inhibitor G?6976 on the SPP-induced PLD activation in myoblasts, where RhoA function was inactivated, was consistent with a dual regulation of the enzyme through RhoA and PKCalpha. Interestingly, the subcellular distribution of PLD isoforms, RhoA and PKCalpha, in SPP-stimulated cells supported the view that the functional relationship between the two PLD regulators, demonstrated to occur in SPP signalling, represents a novel mechanism of regulation of specifically localized PLD.     

The Rice α-Amylase Glycoprotein Is Targeted from the Golgi Apparatus through the Secretory Pathway to the Plastids

The well-characterized secretory glycoprotein, rice (Oryza sativa) α-amylase isoform I-1 (AmyI-1), was localized within the plastids and proved to be involved in the degradation of starch granules in the organelles of rice cells. In addition, a large portion of transiently expressed AmyI-1 fused to green fluorescent protein (AmyI-1-GFP) colocalized with a simultaneously expressed fluorescent plastid marker in onion (Allium cepa) epidermal cells. The plastid targeting of AmyI-1 was inhibited by both dominant-negative and constitutively active mutants of Arabidopsis thaliana ARF1 and Arabidopsis SAR1, which arrest endoplasmic reticulum-to-Golgi traffic. In cells expressing fluorescent trans-Golgi and plastid markers, these fluorescent markers frequently colocalized when coexpressed with AmyI-1. Three-dimensional time-lapse imaging and electron microscopy of high-pressure frozen/freeze-substituted cells demonstrated that contact of the Golgi-derived membrane vesicles with cargo and subsequent absorption into plastids occur within the cells. The transient expression of a series of C-terminal-truncated AmyI-1-GFP fusion proteins in the onion cell system showed that the region from Trp-301 to Gln-369 is necessary for plastid targeting of AmyI-1. Furthermore, the results obtained by site-directed mutations of Trp-302 and Gly-354, located on the surface and on opposite sides of the AmyI-1 protein, suggest that multiple surface regions are necessary for plastid targeting. Thus, Golgi-to-plastid traffic appears to be involved in the transport of glycoproteins to plastids and plastid targeting seems to be accomplished in a sorting signal–dependent manner.     

Enhanced Utilization of Phosphonate and Phosphite by Klebsiella aerogenes

Klebsiella aerogenes ATCC 9621 was able to utilize phosphonates (P_n), including aminoethylphosphonate, ethylphosphonate, methylphosphonate (MP_n), and phosphonoacetate, and inorganic phosphite (P_t) as sole sources of phosphorus (P). The products of the phn gene cluster were absolutely required for P_n breakdown and P_t oxidation to inorganic phosphate (P_i) in this organism. To determine if K. aerogenes ATCC 9621 could be engineered to enhance the utilization of P_n and P_t, a multicopy plasmid, pBI05, which carried the entire phn gene cluster, was introduced into this strain. Despite the increased dosage of the phn genes, K. aerogenes ATCC 9621(pBI05) could utilize only up to 1.1-fold more P_n and P_t than did the control strain with the parent vector alone. These results suggested that P_i, which was generated from P_n and P_t, might limit further utilization of these P compounds. Consequently, to convert the resulting P_i to polyphosphate (polyP), the plasmid pKP28, which carried the K. aerogenes ppk gene (which encodes polyP kinase), was introduced into K. aerogenes ATCC 9621(pBI05). Overexpression of the ppk gene in K. aerogenes ATCC 9621(pBI05, pKP28) resulted in a 2.5-fold increase in P_t utilization over that of the control strain. This recombinant strain also accumulated approximately sixfold more P than did the control strain when the cells were grown with MP_n as a sole source of P.