Genetic comparisons of temperature tolerances of a candidate sea vegetable crop, Alaria esculenta

Genetic comparisons of temperature tolerances of a candidate sea vegetable crop, Alaria esculenta

Summary

Macroalgae are a $6.4 billion global industry, mostly produced through aquaculture rather than wild harvest (FAO 2014). Alaria esculenta has potential in US markets due to its nutritious, palatable characteristics; however, it is necessary to establish temperature-tolerant seedstock and determine crop yield potential (and grow-out requirements) that take sea surface warming attributable to climate change into consideration in order to aid local aquaculture. I have successfully cultured individual genotypes of this kelp to examine the direct effect of temperature on this potential crop. I have also created a representative reproductive phonological profile for wild Alaria esculenta throughout the Gulf of Maine, to determine when seedstock can be available to the industry. Transcriptomic analyses and techniques have been adjusted for a more in-depth analysis of gene expression response to warming sea surface temperatures. Our crops are being produced on a sea farm with success, and I plan to have more specific marker genes in the near future that will allow for the selection of economical and temperature-tolerant strains, aiding the future of the sea vegetable industry in the Gulf of Maine.

Objectives/Performance Targets

Focus has been on Objectives 1, 3, and 4 during 2015.

Objective 1: Identify temperature-tolerant (TT) seedstock strains of Alaria esculenta gametophytes for Maine sea vegetable aquaculture (SVA). During strain identification, regional differences can be determined.

• • Sites have been identified; samples have been collected, cleaned, and released. Cultures are being maintained to gain vegetative mass.

• • With the assistance at the University of Maine Satellite Oceanography Data Lab, I performed a sea surface temperature (SST) comparative analysis of my northern (Lubec) and southern (Two Lights) sites. The median temperatures are plotted from 1985 to 2014, and the overall averages are displayed in Figure 1. It is clear that the two selected locations will allow for a good comparison of, not only colder and warmer average SSTs, but also how the range and variability of temperature fluctuation (higher in the south, steadier in the north) may affect Alaria kelp aquaculture in the future.

Objective 3: Determine which temperature-responsive genes are associated with temperature tolerance (i.e. examine differences in gene expression).

• • While the tissue has yet to be analyzed, I have compiled a list of candidate genes that may be expected to respond to temperature based on work on other phaeophytes: analyses of the Saccharina genome (Ye et al. 2015), and gene expression analyses of Fucus vesiculosus (Jueterbock et al. 2014) and Ectocarpus siliculosus (Dittami et al. 2009). These genes are involved in the following processes: glucose metabolism, vesicular transport, photosynthesis, protein chaperoning, defense mechanisms, etc.

Objective 4: Promote sea vegetable aquaculture in Maine by attending conferences and forums and working directly with harvesters.

• • I attended the 54^th Annual Northeast Algal Society (NEAS) Symposium in Syracuse, NY where I presented a poster of my work, exploring the natural reproductive phenology of Alaria esculenta.

• • I attended the 6^th European Phycological Congress in London, UK. While I presented work from another project in my dissertation, I discussed my work with other scientists to gain insights and direction in my sea vegetable aquaculture project about Alaria esculenta.

• Figure 1

Accomplishments/Milestones

At NEAS, I presented the results from my reproductive phonological surveys to better determine the natural reproductive cycles of Alaria esculenta in the Gulf of Maine. A two-factor analysis of variance showed that Alaria was reproductive virtually year-round, an unexpected discovery. We also showed that there was no difference in reproductive proportion of populations in northern (LUB), mid- (SCH), or southern (PEM) regions (F(2,3) = 0.47, p = 0.67), which may mean that wild Alaria seedstock can be made available to sea farmers year round from any location within the Gulf of Maine. Figure 2 shows the proportion of reproductive Alaria in the three regions.

Other mixed-genotype lines of Alaria esculenta are successfully being grown at our sea farm, demonstrating that our hybrids may have similar success in the future (see Figure 3). Grow-out is consistant and the crops are of good quality.

• Figure 2
• Figure 3

Impacts and Contributions/Outcomes

I have developed a working relationship with the new director of the Center for Biotechnology and Genomics at Texas Tech. We are working out plans so that I may be able to do some of my genomics work at/through this facility, cutting cost and allowing my project to include a time series, to determine how these Alaria esculenta genes are responding to increased temperature in real time. This is an incredible opportunity. This will redirect my gene expression analysis towards one strain per location (northern and southern) in order to gain a deeper understanding of what the gene response is to temperature in my kelp.

However, I can also include more strains in my analysis, as I have secured additional funding for this project through an NSF EPSCORE grant. While this grant is for mostly graduate student support costs, it provides me with small funds to support the use of quantitative PCR to analyze additional strains of Alaria in seeing if the same gene response to temperature is present in various strains. This SARE grant has opened up amazing opportunities and directions for my projects.

Lastly, while this has caused a delay in my gene expression analysis, an unexpected success has occurred based on my selected methods. I proposed and succeeded at culturing specifically selected strains of Alaria esculenta, as planned. Yet this process has been slower than intended. While talking to colleagues at the European Phycological Congress about ways to speed up the growth of my tissue, I now understand why my work is delayed. While the process of culturing Alaria gametopytes and vegetatively growing them up is already well established, no one, to my knowledge, has ever successfully grown up and cultured an individual genotype from one cell. My work is the first of its kind in Alaria and will be instrumental in determining that the differences in gene expression are truly a response to temperature alone, and not variability across multiple genotypes, as has been the case in others’ research.

Collaborators: