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High source-sink ratio at and after sink capacity formation promotes green stem disorder in soybean.

ABSTRACT: Green stem disorder (GSD) of soybean is characterized by delayed leaf and stem maturation despite normal pod maturation. Previous studies have suggested that GSD occurrence is promoted by a high source-sink ratio, which is produced by thinning or shade removal at the R5 growth stage (the beginning of seed filling). Here the effects of different times and durations of shade removal after the R5 stage on GSD severity were analyzed. First, shade removal for more than 28 days after R5 increased GSD severity by more than 0.4 point in GSD score. Thinning treatment at R5 increased specific leaf weight by 23%, suppressed stem dry weight reduction, and upregulated 19 genes including those encoding vegetative storage proteins at R5 + 28d, indicating excess source ability relative to sink size. On the contrary, shade removal for 14 days after R5 decreased GSD severity by 0.5 point in GSD score. In this treatment, seed size was smaller, while seed number was significantly larger than control, suggesting that shortage of source ability relative to sink size. These results implied that soybean plants regulate GSD occurrences either positively or negatively according to a source-sink ratio during the R5 to R5 + 28d growth stages.

SUBMITTER: Yamazaki R

PROVIDER: S-EPMC9213405 | biostudies-literature | 2022 Jun

REPOSITORIES: biostudies-literature

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High source-sink ratio at and after sink capacity formation promotes green stem disorder in soybean.

Yamazaki Ryo R Katsube-Tanaka Tomoyuki T Ogiso-Tanaka Eri E Kawasaki Yohei Y Shiraiwa Tatsuhiko T

Scientific reports 20220621 1

Green stem disorder (GSD) of soybean is characterized by delayed leaf and stem maturation despite normal pod maturation. Previous studies have suggested that GSD occurrence is promoted by a high source-sink ratio, which is produced by thinning or shade removal at the R5 growth stage (the beginning of seed filling). Here the effects of different times and durations of shade removal after the R5 stage on GSD severity were analyzed. First, shade removal for more than 28 days after R5 increased GSD ...[more]

PMID: 35729247

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Project description:Responses to altered source–sink balance have been characterized in many crops at the physiological level, but the underlying genetic and molecular mechanisms are largely unknown. Detailed transcriptional profiling was performed in partially defoliated and shaded tomato plants to explore the effect of reduced source-to-sink ratio on molecular changes in the remaining source leaves. Transcription profiles of the remaining leaves 48 h after partial defoliation or partial shading were compared to leaves of control plants. Common significantly altered genes in the two treatments were assumed to be related to the reduced source-to-sink ratio. Sets of major genes in the abscisic acid, ethylene and gibberellin signal-transduction pathways were downregulated by both treatments. On the other hand, genes encoding cytokinin biosynthesis were upregulated. Most genes coding for transcription factors were also downregulated, especially those related to biotic and abiotic stress responses. Perhaps the most pronounced effect of reduced source-to-sink ratio was related to genes involved in the regulation of photosynthetic activity. Numerous genes coding for light-harvesting proteins, as well as those encoding plastocyanin, ferredoxin and ferredoxin NADP+ oxidoreductase were upregulated. Direct spectrophotometric analyses showed higher maximal potential activity of photosystem I with reduced source-to-sink ratio. As expected, the increased capacity for photosynthetic activity was associated with upregulation of almost all genes coding for the Calvin–Benson cycle and those encoding ATP biosynthesis in the mitochondria. Numerous transcriptional changes were observed 48 h after reducing source-to-sink ratio. Major genes in the photosynthetic-activity pathways were upregulated, whereas those in the pathways of defense mechanisms and responses to stress were downregulated. Genes involved in leaf senescence were also downregulated, suggesting that in addition to increased photosynthetic activity, the remaining leaves undergo a process of rejuvenation.

Project description:BackgroundShading includes low light intensity and varying quality. However, a low red/far-red (R/Fr) ratio of light is a signal that affects plant growth in intercropping and close- planting systems. Thus, the low R/Fr ratio uncoupling from shading conditions was assessed to identify the effect of light quality on photosynthesis and CO2 assimilation. Soybean plants were grown in a growth chamber with natural solar radiation under four treatments, that is, normal (N, sunlight), N + Fr, Low (L) + Fr, and L light.ResultsLow R/Fr ratio significantly increased the total biomass, leaf area, starch and sucrose contents, chlorophyll content, net photosynthetic rate, and quantum efficiency of the photosystem II compared with normal R/Fr ratio under the same light level (P < 0.05). Proteomic analysis of soybean leaves under different treatments was performed to quantify the changes in photosynthesis and CO2 assimilation in the chloroplast. Among the 7834 proteins quantified, 12 showed a > 1.3-fold change in abundance, of which 1 was related to porphyrin and chlorophyll metabolism, 2 were involved in photosystem I (PS I), 4 were associated with PS II, 3 proteins participated in photosynthetic electron transport, and 2 were involved in starch and sucrose metabolism. The dynamic change in these proteins indicates that photosynthesis and CO2 assimilation were maintained in the L treatment by up-regulating the component protein levels compared with those in N treatment. Although low R/Fr ratio increased the photosynthetic CO2 assimilation parameters, the differences in most protein expression levels in N + Fr and L + Fr treatments compared with those in N treatment were insignificant. Similar trends were found in gene expression through quantitative reverse transcription polymerase chain reaction excluding the gene expression of sucrose synthase possible because light environment is one of the factors affecting carbon assimilation.ConclusionsLow R/Fr ratio (high Fr light) can increase the photosynthetic CO2 assimilation in the same light intensity by improving the photosynthetic efficiency of the photosystems.

Dataset Information

High source-sink ratio at and after sink capacity formation promotes green stem disorder in soybean.

Publications

High source-sink ratio at and after sink capacity formation promotes green stem disorder in soybean.

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