Multi-microscopy techniques combined with FT-IR spectroscopy reveals the histological and biochemical causes leading to fruit texture difference in oriental melon (Cucumis melo var. Makuwa Makino).

Multi-microscopy techniques and Fourier transform infrared (FT-IR) spectroscopy were used in this study to investigate the intrinsic causes leading to fruit texture difference between two cultivars of oriental melon 'HDB' (crisp) and 'HPM' (mealy). On the histological aspect, orderly arranged regular-shaped cells with tissue natural fracture pattern showed cell rupture in 'HDB' versus loosely arranged irregular-shaped cells with tissue natural fracture pattern showed cell-to-cell separation in 'HPM' of sarcocarp are histological causes for crisp and mealy fruit texture, respectively. On the biochemical aspect, FT-IR spectra (4000-850 cm-1) of sarcocarp tissue cell wall materials (CWM) happened a dramatic change at the mature stage in 'HPM', but not in 'HDB'. Insightly, the lower de-methyl-esterified homogalacturonan (HG) abundance with higher water-soluble pectin (WSP) ratio and lower hemicellulose (HC) content contribute a poor intercellular adhesion in 'HPM' middle lamella (ML) at the mature stage compared to 'HDB'.

Beta-galactosidase gene family genome-wide identification and expression analysis of members related to fruit softening in melon (Cucumis melo L.).

BACKGROUND: Texture quality is impotent for melon (Cucumis melo L.) fruit. ß-galactosidase (ß-Gal, EC 3.2.1.23) is an important cell wall glycosyl hydrolase involved in fruit softening, However, the ß-Gal gene (BGALs) family hasn't been identified genome-wide in melon. Thus, it's necessary to conduct an in-depth bioinformatic analysis on melon BGALs family and to seek out the key members who participated in melon fruit softening. RESULTS: A total of 21 BGALs members designated as CmBGAL1-CmBGAL21 were identified genome-wide in melon, clustered into A-G seven clades. Among them, three duplications CmBGAL1:CmBGAL3, CmBGAL19:CmBGAL21, and CmBGAL20:CmBGAL21 happened. For conserved domains, besides the Glyco_hydro_35 domain (PF01301), all the members also contained the GHD domain (PF17834) except for CmBGAL12, and the Gal_Lectin (PF02140) domain existed in most CmBGALs at the C-termini. Motifs, protein secondary and tertiary structure analysis showed that the CmBGAL12 is a unique member. Moreover, protein-protein association network analysis showed that the CmBGAL12 is the only node protein. Furthermore, spatiotemporal expression pattern analysis by quantitative real-time PCR (qRT-PCR) suggested that most of CmBGALs expressed in tissues with vigorous cell wall remodeling/disassembly. In addition, cis-acting regulatory elements analysis in promoters inferred that CmBGALs might participate in diverse responsiveness to phytohormone, biotic and abiotic signaling. CONCLUSIONS: A novel clade of CmBGAL members (Clade F) related to melon fruit softening was discovered, since their expression showed a specific surge in the mature fruit of 'HPM' with mealy texture (softening sharply), but not in 'HDB' with crisp texture (softening bluntly). The homologous CmBGAL7-11 in Clade F exhibited identical spatiotemporal expression patterns may multiple genes leading to melon fruit softening.