Gene Expression Differences between High-Growth Populus Allotriploids and Their Diploid Parents

Shiping Cheng,Xiaohu Zhu,Yun Li,Xiangyang Kang,Ting Liao,Yujing Suo,Pingdong Zhang,Pengqiang Yao,Jun Wang

doi:10.3390/f6030839

Abstract

Polyploid breeding is important in Populus genetic improvement programs because polyploid trees generally display increased height growth compared to their diploid parents. However, the genetic mechanism underlying this phenomenon remains unknown. In the present study, apical bud transcriptomes of vigorous, fast growing Populus allotriploid progeny genotypes and their diploid parents were sequenced and analyzed. We found that these allotriploids exhibited extensive transcriptomic diversity. In total, 6020 differentially expressed genes (DEGs) were found when the allotriploid progeny and their parents were compared, among which 791 overlapped between the allotriploids and both parents. Many genes associated with cell differentiation and meristem development were preferentially expressed in apical buds of the fast growing Populus allotriploids compared to their diploid parents. In addition, many auxin-, gibberellin-, and jasmonic acid-related genes were also preferentially expressed in the allotriploids compared to their parents. Our findings show that allotriploidy can have considerable effects on duplicate gene expression in Populus. In particular we identified and considered DEGs that provide important clues for improving our mechanistic understanding of positive heterosis of vigor- and growth-related traits in Populus allotriploids.

Highlights

Polyploidization has played an important role in plant evolution and speciation [1]
We used RNA-Seq to trace the transcriptomic changes between Populus allotriploid progeny and their diploid parents, finding numerous differentially expressed genes that can be used to investigate the molecular mechanism(s) underlying the variation and adaptation resulting from allopolyploidization
The transcripts related to metabolism were significantly enriched in high-growth allotriploids progeny relative to their diploid parents, which indicated that metabolism was the most up-regulated function in heterosis for growth-related traits in these Populus allotriploids

Summary

Introduction

Polyploidization has played an important role in plant evolution and speciation [1]. Polyploids are typically grouped into allopolyploids and autopolyploids when multiple chromosome sets are derived from different species or the same species, respectively [2]. Allopolyploids have succeeded in overcoming the limitations of polyploidy and may exhibit selective advantages, possibly attributable in part to heterozygosity and gene redundancy [3]. Polyploidization can be an important breeding strategy when seeking to develop new tree varieties for forestry purposes. Propagation of polyploid trees is usually accomplished using vegetative organs, and many species are amenable to vegetative (asexual) propagation. This approach is advantageous because it avoids fertility/reproductive problems inherent in polyploids. Once new tree varieties are successfully identified and developed, long-term and sustainable cultivation is possible. Triploid breeding represents a powerful approach toward genetic improvement of Populus [8,9]

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