Identification and Characterization of a Plastidic Adenine Nucleotide Uniporter (OsBT1-3) Required for Chloroplast Development in the Early Leaf Stage of Rice

Daoheng Hu,Wenbin Jin,Yang Li,Qiong He,Yangsheng Li,Hanyu Gong

doi:10.1038/srep41355

Abstract

Chloroplast development is an important subject in botany. In this study, a rice (Oryza sativa) mutant exhibiting impairment in early chloroplast development (seedling leaf albino (sla)) was isolated from a filial generation via hybridization breeding. The sla mutant seedlings have an aberrant form of chloroplasts, which resulted in albinism at the first and second leaves; however, the leaf sheath was green. The mutant gradually turned green after the two-leaf stage, and the third leaf was a normal shade of green. Map-based cloning indicated that the gene OsBT1-3, which belongs to the mitochondrial carrier family (MCF), is responsible for the sla mutant phenotype. OsBT1-3 expression was high in the young leaves, decreased after the two-leaf stage, and was low in the sheath, and these findings are consistent with the recovery of a number of chloroplasts in the third leaf of sla mutant seedlings. The results also showed that OsBT1-3-yellow fluorescent protein (YFP) was targeted to the chloroplast, and a Western blot assay using a peptide-specific antibody indicated that OsBT1-3 localizes to the chloroplast envelope. We also demonstrated that OsBT1-3 functions as a unidirectional transporter of adenine nucleotides. Based on these findings, OsBT1-3 likely acts as a plastid nucleotide uniporter and is essential for chloroplast development in rice leaves at the young seedling stage.

Highlights

Nucleotides are among the most essential cellular components for plant growth, development, and metabolism[1] and are required for the synthesis of DNA and RNA
This subfamily can be subdivided into three groups: first, mitochondrial ADP/ATP carriers (AACs) and AAC-related proteins; second, carriers involved in adenine nucleotide transport; and third, plastidial net adenine nucleotide transporters and brittle proteins[10]
Two transporters (StBT1 and AtBT1) belonging to pANT1s have been well characterized, and both are derived from dicotyledons

Summary

Introduction

Nucleotides are among the most essential cellular components for plant growth, development, and metabolism[1] and are required for the synthesis of DNA and RNA. The first MCF subfamily is important for adenine nucleotide transport between different organelles and the cytosol This subfamily can be subdivided into three groups: first, mitochondrial ADP/ATP carriers (AACs) and AAC-related proteins; second, carriers involved in adenine nucleotide transport; and third, plastidial net adenine nucleotide transporters and brittle proteins[10]. The amino acid sequences of the proteins of the second group present infrequent albeit important similarities to the proteins in the first group, and two members have been reported to exchange adenine nucleotides or related compounds[10] One of these members, ADNT1, is located in the mitochondria and plays a role as a transporter that exports ATP in a counter-exchange with AMP13. None of the members of pANT2s have been characterized in detail at the physiological or biochemical level

Methods

Results

Conclusion