Global Survey and Expressions of the Phosphate Transporter Gene Families in Brassica napus and Their Roles in Phosphorus Response.

Jin Yang,Ming-Ming Liu,Mang-Mang Wang,Peng-Feng Li,Yun-Zhuo Ke,Hong-Jun Zhou,Jie Zhou,Jia-Na Li,Hai Du

doi:10.3390/ijms21051752

Jin Yang, Ming-Ming Liu + Show 7 more

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https://doi.org/10.3390/ijms21051752

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Abstract

Phosphate (Pi) transporters play critical roles in Pi acquisition and homeostasis. However, currently little is known about these genes in oil crops. In this study, we aimed to characterize the five Pi transporter gene families (PHT1-5) in allotetraploid Brassica napus. We identified and characterized 81 putative PHT genes in B. napus (BnaPHTs), including 45 genes in PHT1 family (BnaPHT1s), four BnaPHT2s, 10 BnaPHT3s, 13 BnaPHT4s and nine BnaPHT5s. Phylogenetic analyses showed that the largest PHT1 family could be divided into two groups (Group I and II), while PHT4 may be classified into five, Groups I-V. Gene structure analysis revealed that the exon-intron pattern was conservative within the same family or group. The sequence characteristics of these five families were quite different, which may contribute to their functional divergence. Transcription factor (TF) binding network analyses identified many potential TF binding sites in the promoter regions of candidates, implying their possible regulating patterns. Collinearity analysis demonstrated that most BnaPHTs were derived from an allopolyploidization event (~40.7%) between Brassica rapa and Brassica oleracea ancestors, and small-scale segmental duplication events (~39.5%) in the descendant. RNA-Seq analyses proved that many BnaPHTs were preferentially expressed in leaf and flower tissues. The expression profiles of most colinearity-pairs in B. napus are highly correlated, implying functional redundancy, while a few pairs may have undergone neo-functionalization or sub-functionalization during evolution. The expression levels of many BnaPHTs tend to be up-regulated by different hormones inductions, especially for IAA, ABA and 6-BA treatments. qRT-PCR assay demonstrated that six BnaPHT1s (BnaPHT1.11, BnaPHT1.14, BnaPHT1.20, BnaPHT1.35, BnaPHT1.41, BnaPHT1.44) were significantly up-regulated under low- and/or rich- Pi conditions in B. napus roots. This work analyzes the evolution and expression of the PHT family in Brassica napus, which will help further research on their role in Pi transport.

Highlights

Phosphorus (Pi) plays a central role in energy metabolism, signal transduction cascades, regulation of enzymes and as a structural element in nucleic acids and phospholipids [1]
We identified 81 PHT genes (PHTs) members in the B. napus genome, which represents the largest PHT gene family identified in plants to date
Given B. napus is an allotetraploid (AnAnCnCn) evolved from a spontaneous hybridization event between B. rapa (AnAn) and B. oleracea (CnCn) about 7500 years ago [31], and that Brassicaceae species experienced a common whole genome triplication (WGT) event during evolution, it was expected that the 21 Arabidopsis PHTs may be expanded to ~60 genes in B. rapa or B. oleracea, and ~120 in B. napus genomes, respectively

Summary

Introduction

Phosphorus (Pi) plays a central role in energy metabolism, signal transduction cascades, regulation of enzymes and as a structural element in nucleic acids and phospholipids [1]. The PHT1 family is the high-affinity Pi transporter which represents a group of Pi carriers usually found in plasma membrane [17] Members of this family play a wide role in Pi uptake and remobilization throughout plant development. Based on the increasing available sequenced genome datasets, the PHT gene families were globally identified and analyzed in many plant species, such as Arabidopsis [25], rice [26], and poplar [27]. Most of these studies merely focus on the PHT1 family, and few reports about the whole PHT family at genome-wide level are available

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