PT  - JOURNAL ARTICLE
AU  - Sarit Weissmann
AU  - Pu Huang
AU  - Koki Furuyama
AU  - Madeline A. Wiechert
AU  - Mitsutaka Taniguchi
AU  - James C. Schnable
AU  - Thomas P. Brutnell
AU  - Todd C. Mockler
TI  - <em>DCT4</em> - a new member of the dicarboxylate transporter family in C<sub>4</sub> grasses
AID  - 10.1101/762724
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 762724
4099  - http://biorxiv.org/content/early/2019/09/13/762724.short
4100  - http://biorxiv.org/content/early/2019/09/13/762724.full
AB  - Malate transport shuttles atmospheric carbon into the Calvin-Benson cycle during NADP-ME C4 photosynthesis. Previous characterizations of several plant dicarboxylate transporters (DCT) showed that they efficiently exchange malate across membranes. Here we identify and characterize a previously unknown member of the DCT family, DCT4, in Sorghum bicolor. We show that SbDCT4 exchanges malate across membranes and its expression pattern is consistent with a role in malate transport during C4 photosynthesis. SbDCT4 is not syntenic to the characterized photosynthetic gene ZmDCT2, and an ortholog is not detectable in the maize reference genome. We found that the expression patterns of DCT family genes in the leaves of Z. mays, and S. bicolor varied by cell type. Our results suggest that sub-functionalization of members of the DCT family for the transport of malate into the bundle sheath (BS) plastids occurred during the process of independent recurrent evolution of C4 photosynthesis in grasses of the PACMAD clade. This study confirms the value of using both syntenic information and gene expression profiles to assign orthology in evolutionarily related genomes.