Auxin transport affects a variety of important growth and developmental processes in plants, including the regulation of shoot and root branching. The asymmetrical localization of auxin influx and efflux carriers within the plasma membrane establishes the auxin gradient and facilitates its transport. REH1, a rice EIR1 (Arabidopsis ethylene insensitive root 1)-like gene, is a putative auxin efflux carrier. Phylogenetic analysis of 32 members of the PIN family, taken from across different species, showed that in terms of evolutionary relationship, OsPIN1 is closer to the PIN1 family than to the PIN2 family. It is, therefore, renamed as OsPIN1 in this study. OsPIN1 was expressed in the vascular tissues and root primordial in a manner similar to AtPIN1. Adventitious root emergence and development were significantly inhibited in the OsPIN1 RNA interference (RNAi) transgenic plants, which was similar to the phenotype of NPA (N-1-naphthylphalamic acid, an auxin-transport inhibitor)-treated wild-type plants. α-naphthylacetic acid (α-NAA) treatment was able to rescue the mutated phenotypes occurring in the RNAi plants. Overexpression or suppression of the OsPIN1 expression through a transgenic approach resulted in changes of tiller numbers and shoot/root ratio. Taken together, these data suggest that OsPIN1 plays an important role in auxin-dependent adventitious root emergence and tillering.
生長素影響植物多種生長發(fā)育過程，包括對地上部和根的側(cè)枝發(fā)生的調(diào)控。流入和流出載體在質(zhì)膜上非對稱的分布建立了生長素的濃度梯度分布，并促進(jìn)了生長素的運(yùn)輸。REH1，一個水稻EIR1（Arabidopsis ethylene insensitive root 1）類似基因，預(yù)測為生長素流出載體。對不同物種PIN基因家族的32個成員進(jìn)行系統(tǒng)發(fā)生分析，發(fā)現(xiàn)從親緣進(jìn)化關(guān)系來看，REH1較之PIN2家族，其和PIN1家族的關(guān)系更近。所以這里將其重命名為OsPIN1。和AtPIN1類似，OsPIN1在維管組織和根原基表達(dá)。在OsPIN1的RNAi轉(zhuǎn)基因株系里，不定根的發(fā)生和發(fā)育被顯著抑制，表現(xiàn)出類似于野生型植株被生長素抑制劑NPA處理后的表型。α-NAA處理可以回復(fù)RNAi轉(zhuǎn)基因植株的表型。過量表達(dá)或抑制表達(dá)OsPIN1，會導(dǎo)致轉(zhuǎn)基因植株分蘗數(shù)目的和根冠比的變化。結(jié)合上述結(jié)果，說明OsPIN1在依賴生長素的不定根和分蘗發(fā)生的過程中起著重要的作用。