Unicellular marine algae have promise for providing sustainable and scalable biofuel feedstocks, although no single species has emerged as a preferred organism. Moreover, adequate molecular and genetic resources prerequisite for the rational engineering of marine algal feedstocks are lacking for most candidate species. Heterokonts of the genus Nannochloropsis naturally have high cellular oil content and are already in use for industrial production of high-value lipid products. First success in applying reverse genetics by targeted gene replacement makes Nannochloropsis oceanica an attractive model to investigate the cell and molecular biology and biochemistry of this fascinating organism group. Here we present the assembly of the 28.7 Mb genome of N. oceanica CCMP1779. RNA sequencing data from nitrogen-replete and nitrogen-depleted growth conditions support a total of 11,973 genes, of which in addition to automatic annotation some were manually inspected to predict the biochemical repertoire for this organism. Among others, more than 100 genes putatively related to lipid metabolism, 114 predicted transcription factors, and 109 transcriptional regulators were annotated. Comparison of the N. oceanica CCMP1779 gene repertoire with the recently published N. gaditana genome identified 2,649 genes likely specific to N. oceanica CCMP1779. Many of these N. oceanica–specific genes have putative orthologs in other species or are supported by transcriptional evidence. However, because similarity-based annotations are limited, functions of most of these species-specific genes remain unknown. Aside from the genome sequence and its analysis, protocols for the transformation of N. oceanica CCMP1779 are provided. The availability of genomic and transcriptomic data for Nannochloropsis oceanica CCMP1779, along with efficient transformation protocols, provides a blueprint for future detailed gene functional analysis and genetic engineering of Nannochloropsis species by a growing academic community focused on this genus.

A pectin methylesterase inhibitor (SolyPMEI) from tomato has been identified and characterised by a functional genomics approach. SolyPMEI is a cell wall protein sharing high similarity with Actinidia deliciosa PMEI (AdPMEI), the best characterised inhibitor from kiwi. It typically affects the activity of plant pectin methylesterases (PMEs) and is inactive against a microbial PME. SolyPMEI transcripts were mainly expressed in flower, pollen and ripe fruit where the protein accumulated at breaker and turning stages of ripening. The expression of SolyPMEI correlated during ripening with that of PME-1, the major fruit specific PME isoform. The interaction of SolyPMEI with PME-1 was demonstrated in ripe fruit by gel filtration and by immunoaffinity chromatography. The analysis of the zonal distribution of PME activity and the co-localization of SolyPMEI with high esterified pectins suggest that SolyPMEI regulates the spatial patterning of distribution of esterified pectins in fruit.