Cryo-Treatment Enhances the Embryogenicity of Mature Somatic Embryos via the lncRNA-miRNA-mRNA Network in White Spruce.

Ying Gao,Ying Cui,Jian Zhao,Xiaoyi Chen,Jinfeng Zhang,Ruirui Zhao,Lisheng Kong

doi:10.3390/ijms23031111

Abstract

In conifers, somatic embryogenesis is uniquely initiated from immature embryos in a narrow time window, which is considerably hindered by the difficulty to induce embryogenic tissue (ET) from other tissues, including mature somatic embryos. In this study, the embryogenic ability of newly induced ET and DNA methylation levels was detected, and whole-transcriptome sequencing analyses were carried out. The results showed that ultra-low temperature treatment significantly enhanced ET induction from mature somatic embryos, with the induction rate from 0.4% to 15.5%, but the underlying mechanisms remain unclear. The newly induced ET showed higher capability in generating mature embryos than the original ET. DNA methylation levels fluctuated during the ET induction process. Here, WGCNA analysis revealed that OPT4, TIP1-1, Chi I, GASA5, GST, LAX3, WRKY7, MYBS3, LRR-RLK, PBL7, and WIN1 genes are involved in stress response and auxin signal transduction. Through co-expression analysis, lncRNAs MSTRG.505746.1, MSTRG.1070680.1, and MSTRG.33602.1 might bind to pre-novel_miR_339 to promote the expression of WRKY7 genes for stress response; LAX3 could be protected by lncRNAs MSTRG.1070680.1 and MSTRG.33602.1 via serving as sponges for novel_miR_495 to initiate auxin signal transduction; lncRNAs MSTRG.505746.1, MSTRG.1070680.1, and MSTRG.33602.1 might serve as sponges for novel_miR_527 to enhance the expression of Chi I for early somatic embryo development. This study provides new insight into the area of stress-enhanced early somatic embryogenesis in conifers, which is also attributable to practical applications.

Highlights

Introduction iationsConifers are important forest species, which are hard to be propagated via organogenesis due to the difficulty in root induction, while somatic embryogenesis provides an efficient propagation means [1,2]
These results revealed that cryo-treatment could enhance the embryogenicity of mature somatic embryos, and the embryonic ability of new embryogenic tissue (NET) induced from the cryo-treated mature somatic embryos was improved
We found that oligopeptide transporter 4 (OPT4), TIP1-1, Chi I, glutathione S-transferase (GST), WRKY transcription factor 7 (WRKY7), and WIN1 genes were closely related to long noncoding RNAs (lncRNAs) MSTRG.33602.1, MSTRG.505746.1, and MSTRG.1070680.1

Summary

Introduction

Conifers are important forest species, which are hard to be propagated via organogenesis due to the difficulty in root induction, while somatic embryogenesis provides an efficient propagation means [1,2]. In order to initiate somatic embryogenesis, immature zygotic embryos were commonly used as explants to induce embryogenic tissue (ET) in conifers. The embryogenicity of embryos declines with the increase in the degree of embryo maturation [3,4]. Though ET could be induced from mature zygotic embryos in very few coniferous species [5,6], the induction rate is generally low. The window of ET induction is important and limited by suitable embryo developmental stages, which are influenced by the weather in different years. Cryopreservation is an important technology for the mass production of elite coniferous species [3,4]. Embryogenic materials need to be stored in liquid nitrogen during

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Discussion

Conclusion