A novel fruit ‘netted-cracking’ (FNC) phenotype was discovered in tomato

Fruit cracking is a main disorder that affects the integrity of the fruit and reduces the commercial value in tomato, as well as in other fleshy fruits. Recently, Chinese researchers cloned a fruit FNC gene in tomato and published the study in the open access journal Frontiers of Agricultural Science and Engineering (FASE) which is published by Higher Education Press.

The authors Taotao Wang and Danqiu Zhang said, they cloned the fruit netted-cracking (FNC) gene and verified its function in introgression line IL4-4 based on phenotypic observation, fine-mapping, construction of transgenic plants and detection of gene expression in the study, the result showed a novel phenotype of fruit netted-cracking in an introgression line IL4-4, which is present in neither donor parent (LA0716) nor receptor parent (M82) in tomato. To reveal the regulation mechanism of phenotype, they made a segregation population of F₂ progenies from the cross of IL4-4 and M82 and determined that the inheritance of fruit netted-cracking phenotype is controlled by a single dominant gene. Further map-based cloning of the FNC locus was assigned to a 230 kb region on chromosome 4 that was annotated as containing 38 ORFs. Sequencing and annotation analysis revealed that FNC was the most likely candidate gene.

Overexpression of alleles both FNC^AC and FNC^IL4-4 showed the phenotype of fruit netted-cracking, and the transcript level of FNC in IL4-4 is significantly higher than that in the control M82, suggesting that the transcript level instead of amino acid mutations of FNC resulted in the gain of function of fruit netted-cracking (Fig. 2). In addition, they tested the expression of FNC in pepper and muskmelon fruits with netted-cracking and non netted-cracking trait. They found that the expression of FNC is higher in netted-cracking species, whether it’s pepper or muskmelon.

Furthermore, cytoplasm and nucleus-localized FNC increase the expression of genes involved in suberin, lignin, lipid, lipid transport and cell wall metabolisms. The findings provide novel genetic insights into fruit netted-cracking, and will promote molecular improvement for cracking resistant varieties.

The corresponding author Zhibiao Ye believes that based on the above analysis, the netted-cracking fruit may be cooperatively regulated by two genetic loci which affect tomato fruit cracking by cis-trans regulation. There is an active trans-regulatory factor but a lack of an active corresponding binding motif in cultivated tomatoes. However, there is an active cis-element but the trans-regulatory factor is inactive in S. pennellii. Both active trans-regulatory elements and active cis-element are present in IL4-4 and the trans-element binds to the cis-element of the FNC promoter to activate its expression. There are likely to be other mechanisms involved in this netted-cracking phenotype and further studies are needed.

Original article

Chunli ZHANG , Taotao WANG , Jing LI, Danqiu ZHANG, Qingmin XIE, Shoaib MUNIR, Jie YE, Hanxia LI, Yongen LU, Changxian YANG, Bo OUYANG, Yuyang ZHANG, Junhong ZHANG, Zhibiao YE. Functional gain of fruit netted-cracking in an introgression line of tomato with higher expression of the FNC gene. Frontiers of Agricultural Science and Engineering, 2021, 8(2): 280–291 DOI: 10.15302/J-FASE-2020374

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Founded in May 1954, Higher Education Press Limited Company (HEP), affiliated with the Ministry of Education, is one of the earliest institutions committed to educational publishing after the establishment of P. R. China in 1949. After striving for six decades, HEP has developed into a major comprehensive publisher, with products in various forms and at different levels. Both for import and export, HEP has been striving to fill in the gap of domestic and foreign markets and meet the demand of global customers by collaborating with more than 200 partners throughout the world and selling products and services in 32 languages globally. Now, HEP ranks among China's top publishers in terms of copyright export volume and the world's top 50 largest publishing enterprises in terms of comprehensive strength.

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About Frontiers of Agricultural Science and Engineering

Frontiers of Agricultural Science and Engineering (FASE) is an international journal, which is aimed to publish papers that advance the understanding of scientific, technological/engineering, socioeconomic, institutional/policy and management factors that drive current and future agricultural productivity and sustainability. Our goal is to use FASE as a platform to foster scientific information flow, stimulate transdisciplinary inquiries that have strong multi-disciplinary connections, and cultivate research and idea exchanges that address agricultural sustainability challenges regionally and globally.                                          

FASE is an open-access journal published quarterly with no page charges. Contributions may include cutting-edge research, science news, commentaries, perspectives, or reviews. In addition to publishing regular review and research articles, the journal also publishes ‘Hot Topic’ issues that focus on strategically selected subject matter of high impact, or emerging concerns to address future agricultural development pathways at regional and global levels, and are guest-edited by scientists in their areas of research. Proposals for special issues are welcome and can be submitted any time.