Reviewer Comments - EERE

2011 Algae Platform Review – Reviewer Comments
Reviewer Comments are direct transcripts of commentary and material provided by the Platform’s
Review Panel. They have not been edited or altered by the Biomass Program.
Reviewer: 3 Criteria Score: 8
Success relates to generating strains with improved TAG accumulation. Identifying genes that enable this
without decreasing overall productivity is the challenge.
Reviewer: 4 Criteria Score: 10
See Overall Impressions text.
Reviewer: 5 Criteria Score: 7
The critical success factors were focused on identifying gene targets. Within this narrow biological focus,
the project presentation included adequate plans to address these factors.
Reviewer: 6 Criteria Score: 8
In the context of understanding metabolic synthesis of lipids in diatoms, the PI has done an excellent job
of laying out the appropriate pathways and metabolic markers. There is no doubt the data produce is and
will be high quality.
Reviewer: 7 Criteria Score: 7
Critical success factors are clear focus on lipid production and accumulation in a real world setting
Presenter Response
Demonstrating genetic manipulations and manipulations of nutrient "checkpoints" and "switches" that are
persistant over many generations of diatoms is important to final success of this excellent basic scientific
work to biofuels' development. Given that GMO algae may not be acceptable in commercial use in open
facilities, characterizing heterotrophic growth in the context of the checkpoints/carbon flux under N and
Si deprivation may be of interest----and trying to find natural switches for the cell cycle that can be
applied w/o transformation.
Response: We appreciate the concern about GMOs, but at this point in the development of algal biofuels
technology, it is not clear whether or not GMOs will be allowed. If we assume the need for GMOs in a
biofuels setting will be as great as is the widespread use of GMOs in food crops and approval for their use
is gained, then this research could directly translate into production strains. If not, then it will still provide
a fundamental basis for understanding that will inform approaches for selection of desirable traits
(potentially using mutagenesis). Regarding heterotrophic growth, we are examining that aspect in another
project (C. cryptica has marginal heterotrophic growth capability). Natural switches for cell cycle arrest
are Si and N limitation.
Given that diatoms reach a cardinal point where sexual reproduction is necessary to restore vegetative
size, how will the genetic transformations and knockdown capability react to the diatom life history? Of
course, some diatoms use vegetative processes to restore the largest cell size of the population, in the
absence of sex, but as the population size decreases, sex is still critical in most species to restore cell size.
Please reflect on these problems in your work.
Response: The reduction in size phenomenon is not universal for diatoms, only those with a higher level
of silicification than average in which the cell wall is highly rigid follow this life cycle process. Many
species do not reduce in size with generation, and it is actually extremely difficult to induce the sexual
cycle in them – they have a strong preference for vegetative reproduction. Our lab has published on the
size reduction question, and provided direct proof that it need not happen (Hildebrand et al. 2007, J.
Phycol. 43, 730–740), and other publications have documented the same. Of particular relevance is that
the species we are focusing on do not undergo size reduction and triggering of the sexual cycle, and many
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