RNA-Seq Provides New Insights into the Molecular Events Involved in “Ball-Skin versus Bladder Effect” on Fruit Cracking in Litchi

Abstract

Fruit cracking is a disorder of fruit development in response to internal or external cues, which causes a loss in the economic value of fruit. Therefore, exploring the mechanism underlying fruit cracking is of great significance to increase the economic yield of fruit trees. However, the molecular mechanism underlying fruit cracking is still poorly understood. Litchi, as an important tropical and subtropical fruit crop, contributes significantly to the gross agricultural product in Southeast Asia. One important agricultural concern in the litchi industry is that some famous varieties with high economic value such as ‘Nuomici’ are susceptible to fruit cracking. Here, the cracking-susceptible cultivar ‘Nuomici’ and cracking-resistant cultivar ‘Huaizhi’ were selected, and the samples including pericarp and aril during fruit development and cracking were collected for RNA-Seq analysis. Based on weighted gene co-expression network analysis (WGCNA) and the “ball-skin versus bladder effect” theory (fruit cracking occurs upon the aril expanding pressure exceeds the pericarp strength), it was found that seven co-expression modules genes (1733 candidate genes) were closely associated with fruit cracking in ‘Nuomici’. Importantly, we propose that the low expression level of genes related to plant hormones (Auxin, Gibberellins, Ethylene), transcription factors, calcium transport and signaling, and lipid synthesis might decrease the mechanical strength of pericarp in ‘Nuomici’, while high expression level of genes associated with plant hormones (Auxin and abscisic acid), transcription factors, starch/sucrose metabolism, and sugar/water transport might increase the aril expanding pressure, thereby resulting in fruit cracking in ‘Nuomici’. In conclusion, our results provide comprehensive molecular events involved in the “ball-skin versus bladder effect” on fruit cracking in litchi.

Comparative Transcriptomic Analyses of Different Jujube Cultivars Reveal the Co-Regulation of Multiple Pathways during Fruit Cracking

“…Our co-expression analysis detected a strong correlation between hormone metabolism and other cracking-related metabolic activities. Consistent with the findings of previous studies on atemoya [ 10 ] and lychee [ 12 , 47 ], we observed that the upregulated expression of ABA-related and IAA-related DEGs in cracking jujube fruits can lead to increased ABA and IAA levels in fruits, which might promote fruit cracking directly or indirectly by upregulating the expression of specific TFs, such as MYB , WRKY , and NAC , to increase growth-related gene expression.…”

“…In another study involving A. thaliana , the expression of the sheepgrass LcMYB4 gene positively regulated the accumulation of soluble sugars in transgenic plants [ 55 ]. Transcription factors regulate plant growth and development by modulating the transcription of specific target genes [ 12 ]. In our study, we revealed a positive correlation between TFs and fruit cracking-related processes.…”

“…Zhu et al [ 5 ] analyzed the transcriptome of the grape cultivar ‘Xiang Fei’ and reported that the genes related to cell wall metabolism and cuticle biosynthesis may play crucial roles in fruit cracking. Wang et al [ 12 ] developed a preliminary model of the molecular events that control fruit cracking in ‘Nuomici’ lychee on the basis of RNA-seq data.…”

Genome-Wide Identification of NAC Transcription Factor Family in Juglans mandshurica and Their Expression Analysis during the Fruit Development and Ripening

“…Fruit development is a complex biological process that involves nutrient formation and secondary product metabolism, directly affecting fruit quality formation and commodity value [59]. Previous studies have found that the development, maturation, senescence and quality formation of fruits are specifically regulated by many environmental and regulatory factors, especially NAC TFs [38].…”

Integrated Methylome and Transcriptome Analysis Provides Insights into the DNA Methylation Underlying the Mechanism of Cytoplasmic Male Sterility in Kenaf (Hibiscus cannabinus L.)

“…Transcription factors are closely related to plant development and responses to the environment [ 36 ]. During the development of male gametes in Arabidopsis thaliana , more than 600 transcription factors interact with each other to form a dynamic regulatory network [ 37 ].…”