Expression profiling of starch metabolism-related plastidic translocator genes in rice

Abstract

The genes encoding the major putative rice plastidic translocators involved in the carbon flow related to starch metabolism were identified by exhaustive database searches. The genes identified were two for the triose phosphate/phosphate translocator (TPT), five for the glucose 6-phosphate/phosphate translocator (GPT) including putatively non-functional ones, four for the phosphoenolpyruvate/phosphate translocator (PPT), three for the putative ADP-glucose translocator (or Brittle-1 protein, BT1), two for the plastidic nucleotide transport protein (NTT), and one each for the plastidic glucose translocator (pGlcT) and the maltose translocator (MT). The expression patterns of the genes in various photosynthetic and non-photosynthetic organs were examined by quantitative real-time PCR. OsBT1-1 was specifically expressed in the seed and its transcript level tremendously increased at the onset of vigorous starch production in the endosperm, suggesting that the ADP-glucose synthesized in the cytosol is a major precursor for starch biosynthesis in the endosperm amyloplast. In contrast, all of the genes for OsTPT, OsPPT, and OsNTT were mainly expressed in source tissues, suggesting that their proteins play essential roles in the regulation of carbohydrate metabolism in chloroplasts. Substantial expression of the four OsGPT genes and the OspGlcT gene in both source and sink organs suggests that the transport of glucose phosphate and glucose is physiologically important in both photosynthetic and non-photosynthetic tissues. The present study shows that comprehensive analysis of expression patterns of the plastidic translocator genes is a valuable tool for the elucidation of the functions of the translocators in the regulation of starch metabolism in rice.

Molecular and Biochemical Analysis of the Plastidic ADP-glucose Transporter (ZmBT1) from Zea mays

“…These results clearly indicate that two BT1 homologues occur in maize, in contrast to one homologue in dicotyledonous plants (15) (Fig. 2) and three homologues in rice (35).…”

“…Southern Blot Analysis of ZmBT1 in Maize-In the light of the differences registered between BT1 gene copy numbers in mono-and dicotyledonous plants based on the rice and Arabidopsis genomes (35,36), we assessed BT1 gene copy numbers in maize by Southern blot analyses. We chose restriction enzymes that do cut either ZmBT1 or the recently published ZmBT1-2 homologue (accession number BT016800).…”

Enhanced sucrose loading improves rice yield by increasing grain size

“…Among the genes involved in Suc biosynthesis in leaves, only the expression of those encoding UDP-Glc pyrophosphorylase 2 (UGP2) and cytosolic Fru-1,6-bisphosphatase 1 (cyFBP1) was increased in pPP2::AtSUC2 plants. We also examined the transcript levels of genes for Suc transporters and carbon metabolism-related plastidic translocators (Toyota et al, 2006;Braun and Slewinski, 2009;Ayre, 2011;Chen et al, 2012). Only the transcript level of the gene encoding Suc transporter OsSUT1 was increased in transgenic plants.…”

RNA interference-mediated silencing of the starch branching enzyme gene improves amylose content in rice

“…Many plant genetic transformation systems have been successively applied, thereby improving starch quality (Ryoo et al, 2007). Excessive expression of starch synthesis related genes, including expression of endogenous genes and foreign genes, have been studied in recent years (Toyota et al, 2006). The AGPP gene glgC16 (regulation of variable configuration is not sensitive) from mutant strains of Escherichia coli 618 was used to transfer a tuber-specific expressed gene promoter into potatoes.…”