Kirk MM, Kirk DL
Exploring germ-soma differentiation in Volvox 
JOURNAL OF BIOSCIENCES 29 (2): 143-152 JUN 2004

Just A, Gruber I, Wober M, et al.
Novel method for the cryopreservation of testicular sperm and ejaculated spermatozoa from patients with severe oligospermia: a pilot study 
FERTILITY AND STERILITY 82 (2): 445-447 AUG 2004

Abstract: 

Objective: To investigate Volvox globator as an easy-to-handle vehicle and as a safe alternative for cryopreservation of functional motile sperm cells.

Design: Prospective, controlled, clinical pilot study.

Setting: Two in vitro fertilization (IVF) outpatient clinics for reproductive medicine.

Patient(s): Fifteen patients with severe male infertility (density <100 motile sperm per milliliter) who were recruited from two IVF programs. The sperm cells were not intended for clinical use after thawing.

Intervention(s): In each case, a predetermined number (n = 8) of motile and morphologically intact sperm cells were injected into each Volvox sphere and then cryopreserved. The quality of the sperm cells and the handling of the Volvox spheres were verified.

Main Outcome Measure(s): Postthaw recovery rate in cases of severe male infertility and the amount of motile sperm after thawing.

Result(s): The postthaw recovery rate was 100%. At least 60% of the sperm cells were motile after thawing.

Conclusion(s): The use of the spherical algae Volvox globator offers a promising, inexpensive, and easy approach to the cryopreservation of functional motile sperm cells. Volvox globator is an alternative in countries that prohibit the destructive use of oocytes, even after fertilization has failed.

Jakobiak T, Mages W, Scharf B, et al.
The bacterial paromomycin resistance gene, aphH, as a dominant selectable marker in Volvox carteri 
PROTIST 155 (4): 381-393 DEC 2004

Abstract:

The aminoglycoside antibiotic paromomycin that is highly toxic to the green alga Volvox carteri is efficiently inactivated by aminoglycoside 3'-phosphotransferase from Streptomyces rimosus. Therefore, we made constructs in which the bacterial aphH gene encoding this enzyme was combined with Volvox cis-regulatory elements in an attempt to develop a new dominant selectable marker - paromomycin resistance (Pm-R) - for use in Volvox nuclear transformation. The construct that provided the most efficient transformation was one in which aphH was placed between a chimeric promoter that was generated by fusing the Volvox hsp70 and rbcS3 promoters and the 3' UTR of the Volvox rbcS3 gene. When this plasmid was used in combination with a high-impact biolistic device, the frequency of stable Pm-R transformants ranged about 15 per 106 target cells. Due to rapid and sharp selection, Pm-R transformants were readily isolated after six days, which is half the time required for previously used markers. Co-transformation of an unselected marker ranged about 30%. The chimeric aphH gene was stably integrated into the Volvox genome, frequently as tandem multiple copies, and was expressed at a level that made selection of Pm-R transformants simple and unambiguous. This makes the engineered bacterial aphH gene an efficient dominant selection marker for the transformation and co-transformation of a broad range of V carteri strains without the recurring need for using auxotrophic recipient strains.

Pappas V, Blakely S, Wetzel M, et al.
Functional analysis of the Volvox asymmetric division protein GlsA 
MOLECULAR BIOLOGY OF THE CELL 15: 218A-218A 1207 Suppl. S NOV 2004

Cheng Q, Miller SM
Cytoplasmic Hsp70 distribution correlates with asymmetric division in the green alga Volvox carteri 
MOLECULAR BIOLOGY OF THE CELL 15: 218A-218A 1206 Suppl. S NOV 2004

Kirk DL

Volvox

CURRENT BIOLOGY, 14, R599-R600; for pdf click here

Nedelcu AM, Marcu O, and Michod RE.

Sex as a response to oxidative stress: A two-fold increase in cellular reactive oxygen species activates sex genes.

P ROY SOC LOND B BIO, 271, 1591-1596; for pdf click here

Abstract:

Organisms are constantly subjected to factors that can alter the cellular redox balance and result in the formation of a series of highly reactive molecules known as reactive oxygen species (ROS). As ROS can be damaging to biological structures, cells evolved a series of mechanisms (e.g., cell-cycle arrest, programmed cell death) to respond to high levels of ROS (i.e., oxidative stress). Recently, we presented evidence that in a facultatively sexual lineage – the multicellular green alga Volvox carteri – sex is an additional response to increased levels of stress, and likely ROS and DNA damage. Here, we show that in V. carteri (i) sex is triggered by a ca. two-fold increase in the level of cellular ROS (induced either by the natural sex-inducing stress, namely heat, or by blocking the mitochondrial electron transport chain with antimycin A), and (ii) ROS are responsible for the activation of sex genes. As most types of stress result in the overproduction of ROS, we believe that our findings will prove to extend to other facultatively sexual lineages, which could be indicative of the ancestral role of sex as an adaptive response to stress and ROS-induced DNA damage.

Nedelcu AM and Michod RE. 

Evolvability, modularity, and individuality during the  transition to multicellularity in volvocalean green algae.

In Schlosser G and Wagner G (eds) “Modularity in development and evolution”. Pp. 466-489. University of Chicago Press. (for pdf click here)