Genome-Wide Identification of the SAUR Gene Family in Wax Gourd (Benincasa hispida) and Functional Characterization of BhSAUR60 during Fruit Development

The wax gourd (Benincasa hispida) is an important vegetable crop whose fruits contain nutrients and metabolites. Small auxin upregulated RNA (SAUR) genes constitute the largest early auxin-responsive gene family and regulate various biological processes in plants, although this gene family has not been studied in the wax gourd. Here, we performed genome-wide identification of the SAUR gene family in wax gourds and analyzed their syntenic and phylogenetic relationships, gene structures, conserved motifs, cis-acting elements, and expression patterns. A total of 68 SAUR (BhSAUR) genes were identified, which were distributed on nine chromosomes with 41 genes in two clusters. More than half of the BhSAUR genes were derived from tandem duplication events. The BhSAUR proteins were classified into seven subfamilies. BhSAUR gene promoters contained cis-acting elements involved in plant hormone and environmental signal responses. Further expression profiles showed that BhSAUR genes displayed different expression patterns. BhSAUR60 was highly expressed in fruits, and overexpression led to longer fruits in Arabidopsis. In addition, the plants with overexpression displayed longer floral organs and wavy stems. In conclusion, our results provide a systematic analysis of the wax gourd SAUR gene family and facilitate the functional study of BhSAUR60 during wax gourd fruit development.     

Evolutionary Analysis and Functional Identification of Clock-Associated PSEUDO-RESPONSE REGULATOR (PRRs) Genes in the Flowering Regulation of Roses

Pseudo-response regulators (PRRs) are the important genes for flowering in roses. In this work, clock PRRs were genome-wide identified using Arabidopsis protein sequences as queries, and their evolutionary analyses were deliberated intensively in Rosaceae in correspondence with angiosperms species. To draw a comparative network and flow of clock PRRs in roses, a co-expression network of flowering pathway genes was drawn using a string database, and their functional analysis was studied by silencing using VIGS and protein-to-protein interaction. We revealed that the clock PRRs were significantly expanded in Rosaceae and were divided into three major clades, i.e., PRR5/9 (clade 1), PRR3/7 (clade 2), and TOC1/PRR1 (clade 3), based on their phylogeny. Within the clades, five clock PRRs were identified in Rosa chinensis. Clock PRRs had conserved RR domain and shared similar features, suggesting the duplication occurred during evolution. Divergence analysis indicated the role of duplication events in the expansion of clock PRRs. The diverse cis elements and interaction of clock PRRs with miRNAs suggested their role in plant development. Co-expression network analysis showed that the clock PRRs from Rosa chinensis had a strong association with flowering controlling genes. Further silencing of RcPRR1b and RcPRR5 in Rosa chinensis using VIGS led to earlier flowering, confirming them as negative flowering regulators. The protein-to-protein interactions between RcPRR1a/RcPRR5 and RcCO suggested that RcPRR1a/RcPRR5 may suppress flowering by interfering with the binding of RcCO to the promoter of RcFT. Collectively, these results provided an understanding of the evolutionary profiles as well as the functional role of clock PRRs in controlling flowering in roses.     

Genome-wide Identification and Characterization of FCS-Like Zinc Finger (FLZ) Family Genes in Maize (Zea mays) and Functional Analysis of ZmFLZ25 in Plant Abscisic Acid Response

FCS-like zinc finger family proteins (FLZs), a class of plant-specific scaffold of SnRK1 complex, are involved in the regulation of various aspects of plant growth and stress responses. Most information of FLZ family genes was obtained from the studies in Arabidopsis thaliana, whereas little is known about the potential functions of FLZs in crop plants. In this study, 37 maize FLZ (ZmFLZ) genes were identified to be asymmetrically distributed on 10 chromosomes and can be divided into three subfamilies. Protein interaction and subcellular localization assays demonstrated that eight typical ZmFLZs interacted and partially co-localized with ZmKIN10, the catalytic α-subunit of the SnRK1 complex in maize leaf mesophyll cells. Expression profile analysis revealed that several ZmFLZs were differentially expressed across various tissues and actively responded to diverse abiotic stresses. In addition, ectopic overexpression of ZmFLZ25 in Arabidopsis conferred hypersensitivity to exogenous abscisic acid (ABA) and triggered higher expression of ABA-induced genes, pointing to the positive regulatory role of ZmFLZ25 in plant ABA signaling, a scenario further evidenced by the interactions between ZmFLZ25 and ABA receptors. In summary, these data provide the most comprehensive information on FLZ family genes in maize, and shed light on the biological function of ZmFLZ25 in plant ABA signaling.     

Changes in the Content of Organic Acids and Expression Analysis of Citric Acid Accumulation-Related Genes during Fruit Development of Yellow (Passiflora edulis f. flavicarpa) and Purple (Passiflora edulis f. edulis) Passion Fruits

Organic acids are key components that determine the taste and flavor of fruits and play a vital role in maintaining fruit quality and nutritive value. In this study, the fruits of two cultivars of passion fruit Yellow (Passiflora edulis f. flavicarpa) and purple (Passiflora edulis f. edulis) were harvested at five different developmental stages (i.e., fruitlet, green, veraison, near-mature and mature stage) from an orchard located in subtropical region of Fujian Province, China. The contents of six organic acids were quantified using ultra-performance liquid chromatography (UPLC), activities of citric acid related enzymes were determined, and expression levels of genes involved in citric acid metabolism were measured by quantitative real-time PCR (qRT-PCR). The results revealed that citric acid was the predominant organic acid in both cultivars during fruit development. The highest citric acid contents were observed in both cultivars at green stage, which were reduced with fruit maturity. Correlation analysis showed that citrate synthase (CS), cytosolic aconitase (Cyt-ACO) and cytosolic isocitrate dehydrogenase (Cyt-IDH) may be involved in regulating citric acid biosynthesis. Meanwhile, the PeCS2, PeACO4, PeACO5 and PeIDH1 genes may play an important role in regulating the accumulation of citric acid. This study provides new insights for future elucidation of key mechanisms regulating organic acid biosynthesis in passion fruit.