Disease relevance of MED4

• Analysis of a metagenomic library from the Sargasso Sea supports this hypothesis; most Prochlorococcus cells in this low-P environment contain the P-acquisition genes seen in MED4, although a number of previously undescribed gene combinations were observed [1].
• Heterologous expression of the two cloned P. marinus MED4 ppa genes in Escherichia coli confirmed this proposal, only the inactive ppa1 product being immunodetected by anti-cyanobacterial sPPase antibodies [2].
• The latter represents an intermediate form between the phycobiliproteins of non-Chl b containing cyanobacteria and an extremely modified beta phycoerythrin as the sole derivative of phycobiliproteins still present in MED4 [3].

High impact information on MED4

• Previous analyses of the differences in pigmentation and gene complement revealed that LL-adapted ecotypes carry a gene cluster to produce a functional phycoerythrin, whereas in the fully sequenced genome of the HL-adapted strain MED4, only a single and free-standing cpeB gene occurs [4].
• We observed that MED4 and SS120 have lost several DNA-repair genes, the absence of which could be related to the mutational bias and the acceleration of amino-acid substitution [5].
• In keeping with their comparative light-dependent physiologies, MED4 has many more genes encoding putative high-light-inducible proteins (HLIP) and photolyases to repair UV-induced DNA damage, whereas MIT 9313 possesses more genes associated with the photosynthetic apparatus [3].

Analytical, diagnostic and therapeutic context of MED4

• First, we used DNA microarrays to identify genes involved in the P-starvation response in two strains belonging to different ecotypes, MED4 (high-light-adapted) and MIT9313 (low-light-adapted) [1].

References