Short panicle1 encodes a putative PTR family transporter and determines rice panicle size.
The architecture of the rice inflorescence, which is determined mainly by the number and length of primary and secondary inflorescence branches, is of importance in both agronomy and developmental biology. The position and number of primary branches are established during the phase transition from vegetative to reproductive growth, and several of the genes identified as participating in this process do so by regulating the meristemic activities of inflorescence. However, little is known about the molecular mechanism that controls inflorescence branch elongation. Here, we report on a novel rice mutant, short panicle1 (sp1), which is defective in rice panicle elongation, and thus leads to the short-panicle phenotype. Gene cloning and characterization indicate that SP1 encodes a putative transporter that belongs to the peptide transporter (PTR) family. This conclusion is based on the findings that SP1 contains a conserved PTR2 domain consisting of 12 transmembrane domains, and that the SP1-GFP fusion protein is localized in the plasma membrane. The SP1 gene is highly expressed in the phloem of the branches of young panicles, which is consistent with the predicted function of SP1 and the sp1 phenotype. Phylogenetic analysis implies that SP1 might be a nitrate transporter. However, neither nitrate transporter activity nor any other compounds transported by known PTR proteins could be detected in either a Xenopus oocyte or yeast system, in our study, suggesting that SP1 may need other component(s) to be able to function as a transporter, or that it transports unknown substrates in the monocotyledonous rice plant.
Li
Shengben
S
National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.
Qian
Qian
Q
Fu
Zhiming
Z
Zeng
Dali
D
Meng
Xiangbing
X
Kyozuka
Junko
J
Maekawa
Masahiko
M
Zhu
Xudong
X
Zhang
Jian
J
Li
Jiayang
J
Wang
Yonghong
Y
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D035264:Flowers / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005816:Genetic Complementation Test; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D012275:Oryza / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D010641:Phenotype; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018749:RNA, Plant / Q000235:genetics
D026901:Membrane Transport Proteins; D010940:Plant Proteins; D018749:RNA, Plant; C043912:peptide permease