Transcriptomic Events Involved in Melon Mature-Fruit Abscission Comprise the Sequential Induction of Cell-Wall Degrading Genes Coupled to a Stimulation of Endo and Exocytosis

Abstract

BackgroundMature-fruit abscission (MFA) in fleshy-fruit is a genetically controlled process with mechanisms that, contrary to immature-fruit abscission, has not been fully characterized. Here, we use pyrosequencing to characterize the transcriptomes of melon abscission zone (AZ) at three stages during AZ-cell separation in order to understand MFA control at an early stage of AZ-activation.Principal FindingsThe results show that by early induction of MFA, the melon AZ exhibits major gene induction, while by late induction of MFA, melon AZ shows major gene repression. Although some genes displayed similar regulation in both early and late induction of abscission, such as EXT1-EXT4, EGase1, IAA2, ERF1, AP2D15, FLC, MADS2, ERAF17, SAP5 and SCL13 genes, the majority had different expression patterns. This implies that time-specific events occur during MFA, and emphasizes the value of characterizing multiple time-specific abscission transcriptomes. Analysis of gene-expression from these AZs reveal that a sequential induction of cell-wall-degrading genes is associated with the upregulation of genes involved in endo and exocytosis, and a shift in plant-hormone metabolism and signaling genes during MFA. This is accompanied by transcriptional activity of small-GTPases and synthaxins together with tubulins, dynamins, V-type ATPases and kinesin-like proteins potentially involved in MFA signaling. Early events are potentially controlled by down-regulation of MADS-box, AP2/ERF and Aux/IAA transcription-factors, and up-regulation of homeobox, zinc finger, bZIP, and WRKY transcription-factors, while late events may be controlled by up-regulation of MYB transcription-factors.SignificanceOverall, the data provide a comprehensive view on MFA in fleshy-fruit, identifying candidate genes and pathways associated with early induction of MFA. Our comprehensive gene-expression profile will be very useful for elucidating gene regulatory networks of the MFA in fleshy-fruit.

Comparative Transcriptional Analysis of Loquat Fruit Identifies Major Signal Networks Involved in Fruit Development and Ripening Process

“…The expression levels of bZIP1 were induced by wounding in tomato leaf [54], and improved by C 2 H 4 in tobacco leaf [55]. HY5 and RF2a (bZIP family) were also detected in the mature-fruit abscission zone of olive [56] and melon [57]. NACs manifested the increase of transcripts in mature or immature fruit abscission zones [58,59].…”

Small RNA and degradome sequencing reveals microRNAs and their targets involved in tomato pedicel abscission

“…Precise control of the auxin signal in AZ cells depends on TIR1, ARF and Aux/IAA transcriptional repressors. The auxin receptor gene TIR1 is mediated by miR393 (TIR1/AFB is a nuclear receptor) and is involved in early induction of melon fruit abscission (Corbacho et al 2013). In tomato abscission, ARF 8-1, ARF14 and ARF17 play an important role in the early stage; auxin may mediate the expression of ARF 8-1 and ARF14, while ethylene may mediate ARF13-1.…”

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Transcriptome Analysis and Identification of Genes Associated with Floral Transition and Flower Development in Sugar Apple (Annona squamosa L.)

“…Transcriptome assembly has been successfully applied to many fruit trees, such as pear, melon, litchi, and Chinese cherry (Bai et al, 2013; Corbacho et al, 2013; Lu et al, 2014; Zhu et al, 2015). In our study, we have constructed independent cDNA libraries of four different flower stages in A. squamosa for Illumina RNA-seq.…”