PubMed · 13825313
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R FROELICH. 1959. [Studies on pumpkin seeds].. https://pubmed.ncbi.nlm.nih.gov/13825313/
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Crop yield is a focal point in plant breeding. Regulation of lateral budding through apical dominance was a central target of crop domestication, directly affecting crop production. The young fruits of Cucurbita pepo, summer squash, are produced on plants characterized by apical dominance and differentiation of a single flower bud per leaf axil. A single recessive mutation, mf, results in differentiation of more than one flower per leaf axil, thereby directly increasing production because of the continual day-to-day harvest of the summer squash crop. Positional cloning of the Cucurbita pepo mf (Cpmf) gene denoted a frameshift mutation in a TCP transcription factor, Cp4.1LG13g07780, as causative for the increase in axillary flowering. Cpmf is an ortholog of a tendril-development TCP gene in other cucurbits, and likewise, the recessive allele of Cpmf is associated with distorted tendril development. Gene function is context dependent, and we propose that multiple flowering is a unique pleiotropic attribute of mutation in a tendril-development gene of C. pepo. Characterization of a C. pepo collection confirmed a significant association of the Cpmf mutation with multiple flowering and showed that the mutant allele is absent in ancestral C. pepo and one of its two cultivated subspecies. The beneficial mutation occurred and was selected after the domestication of the other subspecies, during its cultivation for young fruit production. We demonstrate the discovery of a causative yield-increasing sequence variant and its practical utilization in breeding. Our findings provide a molecular target for creation of high-yielding, multiple-flowering summer squash cultivars through marker-assisted breeding or precise genome editing.
In prior studies we learned that colonization of soil can be as important as colonization of roots in determining mycorrhizal influence on the water relations of host plants. Here we use a path analysis modeling approach to test (a) whether quantity of hyphae in soil contributes to variations in stomatal behavior and soil drying, and (b) whether soil colonization or root colonization has a stronger influence on these stomatal and soil drying responses. Experiments were performed on Sorghum bicolor and Cucurbita pepo, with soils and roots colonized by a mixture of Glomus intraradices and Gigaspora margarita. Soil colonization generally made more significant contributions to stomatal conductance than did root colonization. Soil colonization did not make significant direct contributions to soil water potential measures (soil water potential at stomatal closure or soil drying rate), whereas root colonization did contribute a potentially important path to each. The findings further support a role for mycorrhization of the soil itself in contributing to the regulation of stomatal behavior of host plants.
Changes in glutathione contents occur in plants during environmental stress situations, such as pathogen attack, as the formation of reactive oxygen species leads to the activation of the antioxidative defence system. As glutathione is synthesized out of its constituents cysteine, glycine, and glutamate the availability of these components will limit glutathione synthesis in plants especially during stress situations and therefore the ability of the plant to fight oxidative stress. To gain a deeper insight into possible limitations of glutathione synthesis during pathogen attack the present investigations were aimed to study how the subcellular distribution of glutathione precursors correlates with the subcellular distribution of glutathione during virus attack in plants. Selective antibodies against cysteine, glutamate, and glycine were used to study the impact of Zucchini yellow mosaic virus (ZYMV) infection on glutathione precursor contents within different cell compartments of cells from Cucurbita pepo (L.) plants with the transmission electron microscope (TEM). Generally, levels of cysteine and glutamate were found to be strongly decreased in most cell compartments of younger and older leaves including glutathione-producing cell compartments such as plastids and the cytosol. The strongest decrease of cysteine was found in plastids (- 54 %) and mitochondria (- 51 %) of younger leaves and in vacuoles (- 37 %) and plastids (- 29 %) of older leaves. The strongest decrease of glutamate in younger leaves occurred in peroxisomes (- 67 %) and nuclei (- 58 %) and in peroxisomes (- 64 %) and plastids (- 52 %) of the older ones. Glycine levels were found to be strongly decreased (- 63 % in mitochondria and - 53 % in plastids) in most cell compartments of older leaves and strongly increased (about 50 % in plastids and peroxisomes) in all cell compartments of the younger ones. These results indicate that low glycine contents in the older leaves were responsible for low levels of glutathione in these organs during ZYMV infection rather than limited amounts of cysteine or glutamate. Glutathione precursors were virtually absent in cell walls and intercellular spaces and play therefore no important role during ZYMV attack in the apoplast. While glutamate was absent in vacuoles, elevated levels of glycine (up to 30 %) and decreased cysteine contents (up to - 37 %) were observed in vacuoles during ZYMV infection. The impact of the present results on the current knowledge about glutathione synthesis and degradation on the cellular level during ZYMV infection are discussed.