Myosin Va Participates in Acrosomal Formation and Nuclear Morphogenesis during Spermatogenesis of Chinese Mitten Crab Eriocheir sinensis

BACKGROUND: The Chinese mitten crab Eriocheir sinensis belongs to the Class Crustacea, Decapoda, Brachyura. The spermatozoon of this species is of aflagellated type, it has a spherical acrosome surrounded by the cup-shaped nucleus, which are unique to brachyurans. For the past several decades, studies on the spermatogenesis of the mitten crab mainly focus on the morphology. Compared with the extensive study of molecular mechanism of spermatogenesis in mammals, relatively less information is available in crustacean species. Myosin Va, a member of Class V myosin, has been implicated in acrosome biogenesis and vesicle transport during spermatogenesis in mammals. In the present study we demonstrate the expression and cellular localization of myosin Va during spermatogenesis in E. sinensis. METHODOLOGY/PRINCIPAL FINDINGS: Western blot demonstrated that myosin Va is expressed during spermatogenesis. Immunocytochemical and ultrastructural analyses showed that myosin Va mainly localizes in the cytoplasm in spermatocytes. At the early stage of spermiogenesis, myosin Va binds to the endoplasmic reticulum vesicle (EV) and proacrosomal granule (PG). Subsequently, myosin Va localizes within the proacrosomal vesicle (PV) formed by PG and EV fusion and locates in the membrane complex (MC) at the mid spermatid stage. At the late spermatid stage, myosin Va is associated with the shaping nucleus and mitochondria. In mature spermatozoon, myosin Va predominates in acrosomal tubule (AT) and nucleus. CONCLUSIONS/SIGNIFICANCE: Our study demonstrates that myosin Va may be involved in acrosome biogenesis and nuclear morphogenesis during spermatogenesis in E. sinensis. Considering the distribution and molecular characteristics of myosin Va, we also propose a hypothesis of AT formation in this species. It is the first time to uncover the role of myosin Va in crustacean spermatogenesis

Dynein light chain 1 functions in somatic cyst cells regulate spermatogonial divisions in Drosophila

Stem cell progeny often undergo transit amplifying divisions before differentiation. In Drosophila, a spermatogonial precursor divides four times within an enclosure formed by two somatic-origin cyst cells, before differentiating into spermatocytes. Although germline and cyst cell-intrinsic factors are known to regulate these divisions, the mechanistic details are unclear. Here, we show that loss of dynein-light-chain-1 (DDLC1/LC8) in the cyst cells eliminates bag-of-marbles (bam) expression in spermatogonia, causing gonial cell hyperplasia in Drosophila testis. The phenotype is dominantly enhanced by Dhc64C (cytoplasmic Dynein) and didum (Myosin V) loss-of-function alleles. Loss of DDLC1 or Myosin V in the cyst cells also affects their differentiation. Furthermore, cyst cell-specific loss of ddlc1 disrupts Armadillo, DE-cadherin and Integrin-βPS localizations in the cyst. Together, these results suggest that Dynein and Myosin V activities, and independent DDLC1 functions in the cyst cells organize the somatic microenvironment that regulates spermatogonial proliferation and differentiation

Adaptability of myosin V studied by simultaneous detection of position and orientation

We studied the structural dynamics of chicken myosin V by combining the localization power of fluorescent imaging with one nanometer accuracy (FIONA) with the ability to detect angular changes of a fluorescent probe. The myosin V was labeled with bifunctional rhodamine on one of its calmodulin light chains. For every 74 nm translocation, the probe exhibited two reorientational motions, associated with alternating smaller and larger translational steps. Molecules previously identified as stepping alternatively 74-0 nm were found to actually step 64-10 nm. Additional tilting often occurred without full steps, possibly indicating flexibility of the attached myosin heads or probing of their vicinity. Processive myosin V molecules sometimes shifted from the top to the side of actin, possibly to avoid an obstacle. The data indicate marked adaptability of this molecular motor to a nonuniform local environment and provide strong support for a straight-neck model of myosin V in which the lever arm of the leading head is tilted backwards at the prepowerstoke angle

Desempenho de taro em função de doses de cama de aviário, sob sistema orgânico de produção Performance of organically grown taro in relation to poultry litter doses

O experimento foi conduzido na Região Serrana do estado do Rio de Janeiro, em Nova Friburgo, com o objetivo de avaliar o efeito da aplicação de doses de "cama" de aviário, como fonte de nitrogênio, sobre o desempenho de taro cultivado organicamente, em sistema plantio direto. O solo da área foi classificado como Cambissolo Háplico. A aveia preta (Avena strigosa) foi usada como pré-cultivo, em rotação de culturas. O delineamento experimental foi de blocos ao acaso com quatro repetições. Os tratamentos foram doses de "cama" de aviário equivalentes a 0; 50; 100 e 200 kg ha-1 de N, aplicadas em cobertura por ocasião da amontoa, realizada aos 120 dias após o plantio da cultura. A adubação de cobertura com "cama" de aviário promoveu aumento significativo na produtividade de taro, que atingiu um valor máximo com a dose de 130 kg ha-1 de N. A aplicação de "cama" de aviário também favoreceu maiores teores de N nos rizomas de taro.<br>An experiment was carried out in Nova Friburgo, located in the mountain region of Rio de Janeiro State, to evaluate the effect of poultry litter doses on the performance of organically grown taro, under no-tillage. The soil of the area was a Haplic Cambisol. Black oat was previously cultivated in the experimental area. The experimental design was of randomized blocks, with four replications. The treatments consisted of 0; 50;100 and 200 kg N ha-1 of poultry litter, applied 120 days after planting. The use of poultry litter promoted a significant increase in taro yield, with a maximum value corresponding to 130 kg ha-1 of N rate of. It also increased the N content of the taro rhizomes