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Abstract Agar and agarose have wide applications in food and pharmaceutical industries. Knowledge on the genome of red seaweeds that produce them is still lacking. To fill the gap in genome analyses of these red algae, we have sequenced the nuclear and organellar genomes of an agarophyte, Gracilaria changii. The partial nuclear genome sequence of G. changii has a total length of 35.8 Mb with 10,912 predicted protein coding sequences. Only 39.4% predicted proteins were found to have significant matches to protein sequences in SwissProt. The chloroplast genome of G. changii is 183,855 bp with a total of 201 open reading frames (ORFs), 29 tRNAs and 3 rRNAs predicted. Five genes: ssr A, leu C and leu D CP76_p173 ( orf 139) and pbs A were absent in the chloroplast genome of G. changii. The genome information is valuable in accelerating functional studies of individual genes and resolving evolutionary relationship of red seaweeds. Highlights • The nuclear and chloroplast genomes of Gracilaria changii were sequenced. • The partial nuclear genome is 35.8 Mb with 10,912 predicted proteins. • The chloroplast genome is 183,855 bp with 201 ORFs, 29 tRNAs and 3 rRNAs. • The associated core microbiome of G. changii was reported. [ABSTRACT FROM AUTHOR]

The effects of sulfate starvation on the agar characteristics of Gracilaria species was investigated by culturing two red algae from Morib, Malaysia, Gracilaria changii and Gracilaria salicornia in sulfate-free artificial seawater for 5 days. The seaweed samples were collected in October 2012 and March 2013, periods which have significant variation in the amount of rainfall. The agar yields were shown to be independent of sulfate availability, with only 0.60-1.20 % increment in treated G. changii and 0.31-1.40 % increment in treated G. salicornia while their gel strengths did not increase significantly (approximately 5-7 %) after sulfate starvation for both species. The gelling and melting temperatures did not vary between control and treated samples from both species, except for the treated G. changii collected in March 2013. The gel syneresis index of G. salicornia collected in March 2013 increased significantly after sulfate deprivation. Sulfate starvation introduced some variations in the content of 3, 6-anhydrogalactose and total sulfate esters, but the changes did not have a pronounced effect on the physical properties of agar. [ABSTRACT FROM AUTHOR]

Red seaweeds of the genus Gracilaria are agarophytes that produce more than 60% of the world's agar supply. Despite the importance of this genus in agar production, the potential of Gracilaria as a candidate for genomic research has been almost unexplored. In this study, a total of 8,088 expressed sequence tags (ESTs) were generated from Gracilaria changii, and clustered into 4922 tentative unique genes (TUGs), of which approximately 35% showed significant matches (bit scores greater than 50 and E-values less than 10-5) to other genes in the databases. Among the TUGs that have significant similarity to the genes in the databases are ESTs corresponding to diverse functional groups such as metabolism, transcription, signalling, translation, transportation, protein folding, sorting, destination and degradation, cell division, cellular processes, replication and repair, cell structure, and miscellaneous. cDNAs involved in diverse metabolic pathways were identified among the EST collection. The presence and frequency of the transcripts allow us to survey the transcriptomic activities of this tropical agarophyte. [ABSTRACT FROM AUTHOR]