Short panicle1encodes a putative PTR family transporter and determines rice panicle size

Abstract

SUMMARYThe 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.

Rice DENSE AND ERECT PANICLE 2 is essential for determining panicle outgrowth and elongation

“…SP1 (SHORT PANICLE 1), which encodes a putative PTR family transporter, was recently cloned. Growth and elongation of panicle are significantly delayed in the sp1 mutant, leading eventually to arrested and faded branches after heading [25].…”

“…Recently, SP1 (SHORT PANICLE 1) has been identified to encode a putative transporter that belongs to the peptide transporter (PTR) family and may function as a nitrate transporter. The sp1 mutant is defective in rice panicle elongation without affecting the initiation or formation of floral meristems [25].…”

Significance of Light, Sugar, and Amino Acid Supply for Diurnal Gene Regulation in Developing Barley Caryopses

“…The diurnal and spatial expression profiles of AAP genes are diverse, and further studies are required to unravel their potential roles in the control of amino acid levels in the developing seeds, as recently described for orthologous AAPs in Arabidopsis and pea (Pisum sativum; Weigelt et al, 2008;Sanders et al, 2009). In addition to amino acids, phloem-derived peptides contribute significantly to the nitrogen status and regulate development in developing seeds (Miranda et al, 2003;Li et al, 2009). The diurnal expression of 11 peptide transporter genes points at a tight diurnal control of the nitrogen status in seeds via peptide import (Supplemental Table S3).…”

Rice TUTOU1 Encodes a Suppressor of cAMP Receptor-Like Protein That Is Important for Actin Organization and Panicle Development

“…The abortion of spikelets usually causes degeneration of floral organs, leading to reduction of rice yield. Spikelet degeneration can occur from the basal or apical end of the panicle and lead to defective, whitish spikelets, and eventually fewer spikelets per panicle (Li et al, 2009;Cheng et al, 2011).…”