De Novo Assembly and Characterization of Pericarp Transcriptome and Identification of Candidate Genes Mediating Fruit Cracking in Litchi chinensis Sonn.

Abstract

Fruit cracking has long been a topic of great concern for growers and researchers of litchi (Litchi chinensis Sonn.). To understand the molecular mechanisms underlying fruit cracking, high-throughput RNA sequencing (RNA-Seq) was first used for de novo assembly and characterization of the transcriptome of cracking pericarp of litchi. Comparative transcriptomic analyses were performed on non-cracking and cracking fruits. A total of approximately 26 million and 29 million high quality reads were obtained from the two groups of samples, and were assembled into 46,641 unigenes with an average length of 993 bp. These unigenes can be useful resources for future molecular studies of the pericarp in litchi. Furthermore, four genes (LcAQP, 1; LcPIP, 1; LcNIP, 1; LcSIP, 1) involved in water transport, five genes (LcKS, 2; LcGA2ox, 2; LcGID1, 1) involved in GA metabolism, 21 genes (LcCYP707A, 2; LcGT, 9; Lcβ-Glu, 6; LcPP2C, 2; LcABI1, 1; LcABI5, 1) involved in ABA metabolism, 13 genes (LcTPC, 1; Ca2+/H+ exchanger, 3; Ca2+-ATPase, 4; LcCDPK, 2; LcCBL, 3) involved in Ca transport and 24 genes (LcPG, 5; LcEG, 1; LcPE, 3; LcEXP, 5; Lcβ-Gal, 9; LcXET, 1) involved in cell wall metabolism were identified as genes that are differentially expressed in cracked fruits compared to non-cracked fruits. Our results open new doors to further understand the molecular mechanisms behind fruit cracking in litchi and other fruits, especially Sapindaceae plants.

Sweet Cherry (Prunus avium L.) PaPIP1;4 Is a Functional Aquaporin Upregulated by Pre-Harvest Calcium Treatments that Prevent Cracking

“…In this regard, the possibility that increased water permeability could be mediated by aquaporins (AQPs) in more susceptible cultivars is a particularly attractive hypothesis. Transcriptomic data in Litchi chinensis suggests that several AQPs are differentially expressed in cracked fruits [16].…”

Transcriptional changes during ovule development in two genotypes of litchi (Litchi chinensis Sonn.) with contrast in seed size

“…In horticultural crops, only in a few cases, transcriptome sequence analysis has been used for the prediction of genes related to fruit development- as in case of Annona squamosa, Musa accuminata , Prunusavium , Pyrusbrets chneideri etc78910. Comparative analysis of transcriptome in litchi has been used to speculate on the processes involved in the regulation of floral initiation by phytohormones, expression of flowering related genes11, genes related to shading stress12, fruit cracking13, reactive oxygen species (ROS) induced abortion of rudimentary leaves14, fruit abscission15, maturation, coloration16, abscission induced by carbohydrate stress17 and fruit ripening after cold storage18. To the best of our knowledge, there is no report on transcription profiling of early stage developing ovules in litchi.…”

Integrative transcriptome and proteome analyses provide new insights into different stages of Akebia trifoliata fruit cracking during ripening

“…Fruit cracking is a complex physiological process that is controlled by numerous genes working together, rather than a single gene directly controlling the process [18,45]. Researchers have found that several cell wall modi cation genes, including β-GAL, β-GLU, PE, and PG are differentially expressed in cracked fruits compared with levels in non-cracking litchi fruits [21]. Downregulation of PpBGAL can delay peach fruit softening by reducing PG and pectin methylesterase activity [46].…”

“…Studies have indicated that different genetic accessions exhibit major differences in cracking resistance, suggesting that genetic factors play important roles in sweet cherry fruit cracking resistance [19]. Studies on fruit cracking have been performed in many species, including tomatoes, litchis, durians, and apples; these studies have suggested that cell wall-modifying proteins, such as polygalacturonases (PGs), pectinesterase (PE), β-galactosidases (β-GALs), expansins (EXPs), and xyloglucan endotransglycosylase proteins [14,[20][21][22], are associated with fruit cracking. The basic helix-loop-helix (bHLH) gene INDEHISCENT regulates Lepidium campestre fruit dehiscence [23].…”