Characterization of rtSHSp13 gene encoding a development protein involved in vesicular traffic in spermiogenesis

A cDNA, designated as rtSH3p13, was isolated from a rat testis cDNA library. It consists of 1463 bp nuclear acids, which encodes a protein of 312 amino acids and was assigned the GenBank accession number AF227439. The deduced rtSH3p13 protein is a truncated isoform of SH3p13 as a result of mRNA alternative splicing. It is mainly expressed in the rat testis, detected in spermatids at the steps 8-19 of spermiogenesis, and found around the acrosome. During postnatal development, rtSH3p13 appears on day 18 and reaches maximum on day 60. Further experimental results suggested that rtSH3p13 forms a complex with activated epidermal growth factor receptor (EGFR) and interacts with synaptojanin I. Surprisingly, similar to SH3 domain, the V region of rtSH3p13 also inhibits endocytosis in CHO cells. Our results reveal a link between an rtSH3p13-synaptojanin-clathrin complex-mediated formation of pits and the process of spermiogenesis.     

Identification and expression of epidermal growth factor gene in mouse testis

INTRODUCTIONEpidermalgrowthfactor(EGF)wasinitiallyisolatedandpurifiedfromthesubmaxillarygland(SMG)ofmalemouse[1].Itisapolypeptidecomposedof53aminoacidresidues[2].Itinfluencescellproliferationanddifferentiationandmodulatesthegrowthanddevelopmentofmammalianorgans[3--7].AnoteworthyfindingisthatextirpationofmouseSMGresultsinamarkedreductionofserumEGFconcentrationassociatedwithanimpairedspermatogenesis[3].ThisfindingsuggeststhatEGFmayregulatespermproductionanddifferentiation.Inhumantest…     

ON THE ROLE OF CALCIUM IONS IN OOCYTE MATURATION IN THE POLYCHAETE CHAETOPTERUS PERGAMENTACEUS*

The germinal vesicle of mechanically released Chaetopterus oocytes disintegrates in natural sea water (NSW), but not in artificial sea water of normal composition (ASW), calcium-free sea water (CaFSW), magnesium-free sea water (MgFSW) or calcium and magnesium-free sea water (CaMgFSW). Several methods of inducing oocyte maturation using chemically well-defined medium have been established. (1) Germinal vesicle breakdown was induced by the treatment of immature oocytes with KCl (60 mM) in ASW or MgFSW. The presence of Ca²⁺ is necessary for inducing oocyte maturation with high potassium concentration. “Differentiation without cleavage” was observed after this treatment. (2) Trypsin (0.3%) induced oocyte maturation in ASW, but not in CaFSW. Oocytes matured in this manner developed to trochophores upon insemination. (3) Immature oocytes, treated with isotonic CaCl₂ for less than 1 min and then transferred to ASW, underwent germinal vesicle breakdown. The oocytes were arrested at the first meiotic metaphase and upon insemination developed to trochophore larvae. (4) Tetracaine (0.4 mM) induced oocyte maturation in the absence of Ca²⁺ in the medium. In ASW, CaFSW or CaMgFSW containing the drug, oocytes were arrested at the first meiotic metaphase, while in MgFSW with tetracaine they developed parthenogenetically up to the 4- and 8-cell stages. The role of calcium in oocyte maturation was established and its importance was discussed based on the results obtained with the different ways of inducing oocyte maturation.     

The Effect of VA Mycorrhizal Infection and Phosphorus Status on Sunflower Hydraulic and Stomatal Properties

Koide, R. 1985. The effect of VA mycorrhizal infection and phosphorusstatus on sunflower hydraulic and stomatal properties.—J. exp. Bot. 36: 1087–1098. Mycorrhizal (M) and non-mycorrhizal (NM) sunflower plants weregrown in a soil of low phosphorus availability (with and withoutphosphorus amendment) and in a soil of moderate phosphorus availability(without phosphorus amendment). Using the Ohm's law analogyand measured leaf water potentials, stem water potentials, andtranspiration rates, hydraulic resistances were calculated forthe whole plant, leaf, and below leaf components. Mycorrhizalinfection (as high as 89%) was shown to have no effect on theintrinsic hydraulic properties of the soil/plant system overa wide range of transpiration rates in either soil when M andNM plants of equivalent root length were compared. When grownin the soil of moderate phosphorus availability, calculatedhydraulic resistances under given environmental conditions werethe same for M and NM plants, as were stomatal resistances andtranspiration rates. When grown in the soil of low phosphorusavailability, calculated values of hydraulic resistance werelower for M plants than for NM plants under given sets of environmentalconditions. These differences in calculated hydraulic resistancewere not due to a difference in the intrinsic hydraulic propertiesof M and NM plants. The differences were evident because stomatalresistances were lower and transpiration rates higher for Mplants and because hydraulic resistance varied inversely withtranspiration rate. When plants of significantly greater rootlength were compared to plants of lesser root length, the calculatedhydraulic resistances under given environmental conditions weremuch lower for the plants of greater root length. This differencewas largely due to a difference in the intrinsic hydraulic propertiesbetween large and small plants, and not because of differencesin transpiration rate. The elevated transpiration rates exhibitedby M plants were attributed to an enhanced phosphorus status.Short term phosphorus amendments made to phosphorus-deficientNM plants improved transpiration; transpiration rates were similarfor M and NM plants before NM plants became phosphorus-deficient,and phosphorus-amended M and NM plants had similar transpirationrates. The data are discussed in relation to other reports ofmycorrhizal influence on hydraulic and stomatal resistances.Possible mechanisms for the influence of infection on stomatalresistance are also briefly discussed. Key words: Hydraulic resistance, stomatal resistance, mycorrhizas     

Mycorrhizal Response of Two Tomato Genotypes Relates to their Ability to Acquire and Utilize Phosphorus

The purpose of this study was to determine how a plant's responseto colonization by mycorrhizal fungi relates to its abilityto acquire and utilize phosphorus for growth and reproduction.Two tomato genotypes previously found to be either responsive(‘LA1709’) or unresponsive (‘large cherry’)to mycorrhizal colonization during early vegetative growth wereexamined in detail. Plants were grown at four levels of addedphosphate or with mycorrhizal inoculum. Vegetative and reproductivegrowth, phosphorus uptake and root length density were measuredduring the course of plant development. Mycorrhizal symbiosissignificantly increased above-ground dry mass, root length,phosphorus content and yield under low phosphorus conditionsin ‘LA1709’, while it had less effect on these characteristicsin ‘large cherry’. When uninfected, however, ‘LA1709’grew and reproduced poorly unless high amounts of phosphoruswere added to the soil, while ‘large cherry’ grewwell under very low phosphorus conditions. This was because‘large cherry’ had significantly higher root lengthdensities than ‘LA1709’, enabling plants from thisgenotype to explore more soil volume and acquire greater amountsof phosphorus when grown without mycorrhizal fungi in low phosphorussoil. ‘Large cherry’ also had higher phosphorususe efficiency and allocated a greater proportion of phosphorusto reproduction when uninfected than ‘LA1709’. Itappears traits that affect a plant's ability to acquire andutilize phosphorus efficiently for growth and reproduction canalso affect its response to mycorrhizal colonization in tomato.Copyright1998 Annals of Botany Company. Tomato,Lycopersicon esculentum,mycorrhiza,Glomus etunicatum,phosphorus, reproduction, lifespan.