Regulation of gametogenesis and zoosporogenesis in Ulva linza (Chlorophyta): comparison with Ulva mutabilis and potential for laboratory culture

Abstract

Green Ulvophyte macroalgae represent attractive model systems for understanding growth, development, and evolution. They are untapped resources for food, fuel, and high-value compounds, but can also form nuisance blooms. To fully analyze green seaweed morphogenesis, controlled laboratory-based culture of these organisms is required. To date, only a single Ulvophyte species, Ulva mutabilis Føyn, has been manipulated to complete its whole life cycle in laboratory culture and to grow continuously under axenic conditions. Such cultures are essential to address multiple key questions in Ulva development and in algal–bacterial interactions. Here we show that another Ulva species, U. linza, with a broad geographical distribution, has the potential to be grown in axenic culture similarly to U. mutabilis. U. linza can be reliably induced to sporulate (form gametes and zoospores) in the laboratory, by cutting the relevant thallus tissue into small pieces and removing extracellular inhibitors (sporulation and swarming inhibitors). The germ cells work as an ideal feed stock for standardized algae cultures. The requirement of U. linza for bacterial signals to induce its normal morphology (particularly of the rhizoids) appears to have a species-specific component. The axenic cultures of these two species pave the way for future comparative studies of algal–microbial interactions.

Cell structure and microtubule organisation during gametogenesis of Ulva mutabilis Føyn (Chlorophyta)

“…Upon removal of the sporulation inhibitors, the gametogenesis of the thalli can be artificially and synchronously initiated ( Stratmann et al 1996, Wichard andOertel 2010). This was also observed in Ulva linza L. (Vesty et al 2015) and Ulva lactuca L. (Wichard and Oertel 2010).…”

Seaweed reproductive biology: environmental and genetic controls

“…SI-2 is excreted into the space between the two cell layers. Gametogenesis or sporogenesis can be induced by cutting the thallus into fragments and subsequent washing as observed in different Ulva species, since this is thought to result in the removal of both sporulation inhibitors (Stratmann et al 1996, Wichard and Oertel 2010, Vesty et al 2015. The SI-2-type sporulation inhibitor forms a gradient from the base to the top of the thallus, resulting in higher percentages of gamete formation and discharge from the apical regions (Wichard and Oertel 2010).…”

Searching for wheat resistance to aphids and wheat bulb fly in the historical Watkins and Gediflux wheat collections

“…Phenotyping of plant collections to search for beneficial plant traits such as resistance to insect pests is a crucial part of developing new germplasm for breeding of elite varieties that will thrive under likely climate change and pesticide constrained conditions. This is increasingly being done on any accessions that could perceivably be useful to crop improvement (Grosskinsky et al , 2015; Rahaman et al , 2015). …”