Transcriptome analysis of differentially expressed genes during anther development stages on male sterility and fertility in Cucumis melo L. line.

The genic male sterility (MS) plays a major role in melon hybrids production, it could reduce the cost of pollination and increase the yield and quality. However, the molecular mechanism underlying genetic male sterility is yet poorly understood. The morphological differences of flower buds of melon were observed showed that the flower buds were tetrad when they were 1 mm stage and monocyte microspore when they were 2 mm stage. Electron microscopy showed that there was significant difference between MS lines and MF (male fertility) lines. In order to detect the global expression of the genes during the melon anther development and association with MS, 12 DEGs (differentially expressed genes) libraries were constructed from the anther of MS and MF in the bud stage with 1 and 2 mm diameter, respectively. A total of 765 DEGs expressed in anther during different developmental stage (MS 1 mm vs. MS 2 mm), 148 and 309 DEGs were found to be related to MS as compared to MF (MS 1 mm vs. MF 1 mm, and MS 2 mm vs. MF 2 mm) at a false discovery rate FDR <0.01. Among these, 10 DEGs were expressed in all the three comparisons, including transcription factor bHLH genes. Among the DEGs in RNA-seq analysis, 28 were validated by qRT-PCR. Of these, a number of genes were involved in ABC transfactor B family, cytochrome-related genes, hormone-related genes (auxin transporter, gibberellin-regulated protein), MADS-box protein genes, F-box protein genes, peroxidase-related, and Zinc finger protein genes. These genes are involved in many biological pathways, including starch and sucrose metabolism, signal transduction mechanisms and transcription factors, etc. Compared to the same developmental stage of MS and MF, the different developmental stages of MS indicated diverse gene regulation pathways involved in the anther development in MS. These results would provide novel insight into the global network to male sterility in melon.

Phloem Loading through Plasmodesmata: A Biophysical Analysis.

In many species, Suc en route out of the leaf migrates from photosynthetically active mesophyll cells into the phloem down its concentration gradient via plasmodesmata, i.e. symplastically. In some of these plants, the process is entirely passive, but in others phloem Suc is actively converted into larger sugars, raffinose and stachyose, and segregated (trapped), thus raising total phloem sugar concentration to a level higher than in the mesophyll. Questions remain regarding the mechanisms and selective advantages conferred by both of these symplastic-loading processes. Here, we present an integrated model-including local and global transport and kinetics of polymerization-for passive and active symplastic loading. We also propose a physical model of transport through the plasmodesmata. With these models, we predict that (1) relative to passive loading, polymerization of Suc in the phloem, even in the absence of segregation, lowers the sugar content in the leaf required to achieve a given export rate and accelerates export for a given concentration of Suc in the mesophyll and (2) segregation of oligomers and the inverted gradient of total sugar content can be achieved for physiologically reasonable parameter values, but even higher export rates can be accessed in scenarios in which polymers are allowed to diffuse back into the mesophyll. We discuss these predictions in relation to further studies aimed at the clarification of loading mechanisms, fitness of active and passive symplastic loading, and potential targets for engineering improved rates of export.

[Effects of potassium level on photosynthetic characteristics and chloroplast submicroscopic structure of muskmelon leaves].

With soilless culture in greenhouse, this paper studied the effects of three potassium (K) levels (120, 240, and 360 mg x L(-1)) on the photosynthetic characteristics and chloroplast submicroscopic structure of muskmelon cv. 'Tiantian No. 1' leaves. The results showed that at low (120 mg x L(-1)) and high (360 mg x L(-1)) K levels, the net photosynthetic rate (Pn) decreased, chloroplast lamellar structure disordered, and lamella number decreased. No significant effects were observed on CO2 compensation point (70 microl x L(-1)), saturation CO2 for photosynthesis (600 microl x L(-1)) and light compensation point (50 micromol x m(-2) x s(-1)) at the three K levels. The saturation light for photosynthesis, carboxylation efficiency and apparent quantum yield at 240 mg x L(-1) K level were significantly higher, being 1200 micromol x m(-2) x s(-1), 0.1364 and 0.0237, respectively. Under the conditions of this study, the optimal K level in the nutrient solution for muskmelon soilless culture was 240 mg x L(-1).

Reducing Salmonella on cantaloupes and honeydew melons using wash practices applicable to postharvest handling, foodservice, and consumer preparation.

Washing conditions that included a soak or brush scrub were evaluated for removal of Salmonella from the surface of smooth (honeydew) or complex (cantaloupe) melon rinds. Melon rinds were spot-inoculated onto a 2.5 cm2 area of rind (squares) with approximately 6.0 log(10) CFU/square of an avirulent nalidixic acid-resistant strain of Salmonella typhimurium. Melons were washed by immersion in 1500 ml of water or 200 ppm total chlorine and allowed to soak or were scrubbed over the entire melon surface with a sterile vegetable brush for 60 s. Inoculated sites, uninoculated sites ("next to" sites) that were adjacent to inoculated sites, and sites on the side of the melon opposite (remote sites) the inoculated site were excised and pummeled in a stomacher for 2 min prior to plating onto tryptic soy or bismuth sulfite agar supplemented with 50 microg/ml nalidixic acid. S. typhimurium was reduced on the rind of cantaloupe by 1.8 log CFU/melon after soaking for 60 s in 200 ppm total chlorine, which was significantly better than the 0.7 log CFU/melon achieved with soaking in water. For both water and 200 ppm total chlorine, scrubbing with a vegetable brush was shown to be significantly (0.9 log CFU/cantaloupe) more effective than soaking alone. When honeydew melons were soaked or scrubbed in water, reductions of 2.8 log CFU/melon or >4.6 log CFU/melon (four of five samples), respectively, were observed. However, when water treatments were used, the presence of Salmonella-positive "next to" and remote sites indicated that bacteria were spread from inoculated site on the rind to uninoculated sites either through the rinse water (40-70 CFU/ml of Salmonella) or scrub brush (400-500 CFU/brush). Transfer to other sites occurred more often with cantaloupe than honeydew melons. This transfer was eliminated when 200 ppm total chlorine was used. When 200 ppm total chlorine was used, Salmonella could not be detected in the water or on the scrub brush. For optimal microbial removal in food service and home settings, melons should be scrubbed with a clean brush under running water. However, to ensure the benefits of brushing, instructions for cleaning and sanitizing brushes must also be emphasized. For food service settings where concentration and pH can be adequately measured, the use of chlorinated water may provide additional benefit.