Biochemical basis of high-temperature inhibition of ethylene biosynthesis in ripening tomato fruits

Biggs, M. S., Woodson, W. R. and Handa, A. K. 1988. Biochemical basis of high-temperature inhibition of ethylene biosynthesis in ripening tomato fruits. Physiol. Plant. 72: 572578
Incubation of fruits of tomato ( Lycopersicon esculentum Mill. cv. Rutgers) at 34°C or above resulted in a marked decrease in ripening-associated ethylene production. High temperature inhibition of ethylene biosynthesis was not associated with permanent tissue damage, since ethylene production recovered following transfer of fruits to a permissive temperature. Determination of pericarp enzyme activities involved in ethylene biosynthesis following transfer of fruits from 25°C to 35 or 40°C revealed that 1-aminocyclopropane-l-carboxylic acid (ACC) synthase (EC 4.4.1.14) activity declined rapidly while ethylene forming enzyme (EFE) activity declined slowly. Removal of high temperature stress resulted in more rapid recovery of ACC synthase activity relative to EFE activity. Levels of ACC in pericarp tissue reflected the activity of ACC synthase before, during, and after heat stress. Recovery of ethylene production following transfer of pericarp discs from high to permissive temperature was inhibited in the presence of cycloheximide, indicating the necessity for protein synthesis. Ethylene production by wounded tomato pericarp tissue was not as inhibited by high temperature as ripening-associated ethylene production by whole fruits.     

Identification of an S-locus glycoprotein allele introgressed from B. napus ssp. rapifera to B. napus ssp. oleifera.

We have previously described a developmentally regulated mRNA in maize that accumulates in mature embryos and is involved in a variety of stress responses in the plant. The sequence of the encoded 16 kDa protein (MA16) predicts that it is an RNA-binding protein, since it possesses a ribonucleoprotein consensus sequence-type RNA-binding domain (CS-RBD). To assess the predicted RNA binding property of the protein and as a starting point to characterize its function we have used ribohomopolymer-binding assays. Here we show that the MA16-encoded protein binds preferentially to uridine- and guanosine-rich RNAs. In light of these results a likely role for this protein in RNA metabolism during late embryogenesis and in the stress response is discussed.     

Reconstructing Ancient Hohokam Irrigation Systems in the Middle Gila River Valley,Arizona, United States of America

We explore the concept of scales to examine emerging irrigation realities, i.e., connecting more agents within larger spaces - relates to the complexity of irrigation systems. Modern hydraulic models allow the inclusion of emerging multi-scale issues over time, including social issues related to different spatial and temporal scales. We show that the time needed to manage irrigation efficiently relates to the size of a system. By reconstructing ancient Hohokam irrigation systems in Arizona, we identify how longer-term extension of spatial scales created management problems beyond the scope of available technology. This approach allows greater understanding of how stresses in daily irrigation management may have impacted longer-term societal stability.     

Pollination-Induced Ethylene in Carnation (Role of Pollen Tube Growth and Sexual Compatibility)

The pollen-pistil interactions that result in the stimulation of ethylene production and petal senescence in carnation (Dianthus caryophyllus L.) flowers were investigated. Pollination of White Sim flowers with Starlight pollen elicited an increase in ethylene production by styles, leading to increased petal ethylene and premature petal senescence. In contrast, pollination with 87-29G pollen led to an early increase in ethylene production, but this was not sustained, and did not lead to petal senescence. Both Starlight and 87-29G pollen germinated on White Sim stigmas and their tubes grew at similar rates, penetrating the length of the style. Crosses between Starlight and White Sim led to the production of viable seeds, whereas 87-29G pollen was infertile on White Sim flowers. Pollination of other carnations with 87-29G elicited ethylene production and petal senescence and led to the production of viable seeds. These results suggest that physical growth of pollen tubes is insufficient to elicit a sustained increase in ethylene production or to lead to the production of signals necessary for elicitation of petal ethylene production and senescence. Rather, the cell-cell recognition reactions leading to sexual compatibility in Dianthus appear to play a role in this interorgan signaling after pollination.     

Molecular cloning and characterization of senescence-related genes from carnation flower petals

The senescence of carnation (Dianthus caryophyllus L.) flower petals is associated with increased production of ethylene which plays an important role in regulating this developmental event. Three senescence-related cDNA clones were isolated from a cDNA library prepared from mRNA isolated from senescing petals. These cDNAs are representative of two classes of mRNAs which increase in abundance in senescing petal tissue. The mRNA for one class is present at low levels during the early stages of development and begins to accumulate in mature petals prior to the increase in ethylene production. The accumulation of this mRNA is reduced, but not eliminated, in petals treated with aminooxyacetic acid, an inhibitor of ethylene biosynthesis, or silver thiosulfate, an ethylene action inhibitor. In contrast, expression of the second class of mRNAs appears to be highly regulated by ethylene. These mRNAs are not detectable prior to the rise in ethylene production and increase in abundance in parallel with the ethylene climacteric. Furthermore, expression of these mRNAs is significantly inhibited by both aminooxyacetic acid and silver thiosulfate. Expression of these mRNAs in vegetative and floral organs was limited to floral tissue, and predominantly to senescing petals.     

Catecholamine-induced hyperglycemia in dogs: independence from alterations in pancreatic hormone release

Although isoproterenol is a very effective hyperglycemic agent in dogs, other species such as rats, baboons and man are resistant to this effect. In each of these species catecholamines exert pronounced effects on insulin and glucagon release from the pancreas. In man, baboons, and rats catecholamine-induced alterations in pancreatic hormone release indirectly influence the hyperglycemic response to these amines: glucagon release supports and insulin release limits hyperglycemic responses. In contrast, the present study demonstrates that in dogs catecholamine-induced hyperglycemic responses are relatively independent of concurrent alterations in pancreatic hormone release. In dogs isoproterenol produces hyperglycemia equal to or greater than responses to epinephrine despite large increases in insulin release produced by isoproterenol. Moreover, catecholamine-induced hyperglycemia is not significantly altered when insulin and glucagon release are blocked with somatostatin.     

Metalloproteinase activities expressed during development and maturation of the rat prostatic complex and seminal vesicles.

The objective of this study was to characterize proteinase activities expressed during development and maturation of the prostate gland and seminal vesicles of the rat by using gelatin-and casein-containing SDS polyacrylamide gel zymography. The prostatic complexes of 2- and 10-day-old animals and the individual lobes of the prostate (ventral, dorsolateral, and anterior [coagulating gland]) and the seminal vesicles of 15-day-old animals expressed prominent gelatinolytic activities of approximately 64, 71, and 76 kDa. These activities had properties of metalloproteinases; i.e., they were stimulated by Ca2+ and inhibited by EDTA and EGTA. They were greatly diminished by 52 days of age (immediately postpuberty) and were not detected in the dorsal lobe of the adult. Less active gelatinolytic proteinases with molecular masses of approximately 34 and 43 kDa were expressed in the developing prostatic complexes and individual lobes and seminal vesicles, but they were not detected in postpubertal animals. Weak gelatinolytic activities of 82, 85, and 89 kDa were found in the prostatic complexes; these activities were greatly diminished in all prostate lobes with sexual maturation but were expressed in the seminal vesicles at all ages. A large-molecular-mass Ca(2+)-independent proteinase of 130 kDa or greater was first detected in the dorsolateral prostate at 21 days of age. This activity was expressed in both the lateral and dorsal lobes of the adult but was greater in the lateral lobe. Proteinase activities of about 22 and 26 kDa that were not stimulated by Ca2+ were detected in the ventral prostate at 15 days of age by means of both gelatin and casein gels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Structural model for an oligonucleotide containing a bulged guanosine by NMR and energy minimization

We present three-dimensional structural models for a DNA oligomer containing a bulged guanosine based on proton NMR data and energy minimization computations. The nonexchangeable proton resonances of the duplex 5'd(GATGGGCAG).d(CTGCGCCATC) are assigned by nuclear Overhauser effect spectroscopy (NOESY) and correlated spectroscopy connectivities, and the NMR spectrum is compared with that of a regular 8-mer of similar sequence, 5'd(GATGGCAG).d(CTGCCATC). Experimental proton-proton distances are obtained from NOESY spectra acquired with mixing times of 100, 150, and 200 ms. A refined three-dimensional structure for the bulge-containing duplex is calculated from regular B DNA starting coordinates by using the AMBER molecular mechanics program [Weiner, S. J., Kollman, P. A., Case, D. A., Singh, U. C., Ghio, C., Alagona, G., Profeta, S., & Weiner, P. (1984) J. Am. Chem. Soc. 106, 765-784]. We compare structures obtained by building the helix in three and four base pair increments with structures obtained by direct minimization of the entire nine base sequence, with and without experimental distance constraints. The general features of all the calculated structures are very similar. The helix is of the B family, with the extra guanine stacked into the helix, and the helix axis is bent by 18-23 degrees, in agreement with gel mobility data for bulge-containing sequences [Rice, J. A. (1987) Ph.D. Thesis, Yale University].