A chromosome‐level genome assembly provides insights into ascorbic acid accumulation and fruit softening in guava (Psidium guajava)

第一作者：Chen Feng

第一单位：中科院华南植物园

通讯作者：Ming Kang

 Abstract 

背景回顾：Guava (Psidium guajava) is an important, fleshy‐fruited tree of the Myrtaceae family that is widely cultivated in tropical and subtropical areas of the world and has attracted considerable attention for the richness of ascorbic acid in its fruits.

提出问题：However, studies on the evolution and genetic breeding potential of guava are hindered by the lack of a reference genome.

主要研究：Here, we present a chromosome‐level genomic assembly of guava using PacBio sequencing and Hi‐C technology.

结果1-组装+注释：We found that the genome assembly size was 443.8 Mb with a contig N50 of ~15.8 Mb. We annotated a total of 25,601 genes and 193.2 Mb of repetitive sequences for this genome. 

结果2-全基因组复制事件：Comparative genomic analysis revealed that guava has undergone a recent whole‐genome duplication (WGD) event shared by all species in Myrtaceae.

结果3-抗坏血酸：In addition, through metabolic analysis, we determined that the L‐galactose pathwayplays a major role in ascorbic acid biosynthesis in guava fruits.

结果4-柔软果质：Moreover, the softening of fruits of guava may result from both starch and cell wall degradation according to analyses of gene expression profiles and positively selected genes.

结论：Our data provide a foundational resource to support molecular breeding of guava and represent new insights into the evolution of soft, fleshy fruits in Myrtaceae.

 摘  要 

番石榴，又称芭乐，是桃金娘科一种重要的肉质果树，广泛种植于全球范围的热带和亚热带地区，因其果实中富含抗坏血酸而广受关注。但是，由于没有一个可供利用的参考基因组，严重阻碍了番石榴演化以及遗传育种方面的研究。本文中，作者基于PacBio测序以及Hi-C技术，报道了番石榴的染色体级别的组装。作者获得的番石榴基因组组装大小约为443.8Mb，其中contig N50约为15.8Mb。作者共注释了25601个基因，而基因组中193.2Mb的序列为重复序列。比较基因组分析显示番石榴基因组中发生了一次全基因组复制事件，并且是由所有桃金娘科物种共享的一次近期的全基因组复制事件。另外，通过代谢分析，作者发现L-半乳糖途径在番石榴果实抗坏血酸的生物合成中扮演着非常重要的作用。此外，基于基因共表达图谱以及正向选择基因分析，番石榴果实的软化可能是由于淀粉和细胞壁的降解所导致的。本文的研究结果为番石榴的分子育种提供了重要的资源，同时也为桃金娘科物种柔软肉质果实的演化提供了新的视野。

 通讯作者 

**康明**

doi: 10.1111/pbi.13498

Journal: Plant Biotechnology Journal

Published date: Oct 24, 2020