Abstract
Broccoli (Brassica oleracea var. italica) is an important vegetable crop rich in vitamins and sulforaphane. However, the floral heads of broccoli experience rapid postharvest senescence. Here we found that hydrogen sulfide (H2S) treatment alleviated dark-promoted senescence in broccoli florets. H2S delayed the symptoms of senescence and maintained higher levels of chlorophyll and Rubisco and lower protease activity compared with water control. Gene expression analysis showed that H2S down-regulated the expression of chlorophyll degradation-related genes BoSGR, BoNYC, BoCLH1, BoPPH, and BoRCCR. Expression of lipoxygenase gene BoLOX1 and the genes involved in the ethylene synthesis pathway, BoACS2 and BoACS3, were also down-regulated by H2S. The reduced expression level in cysteine protease gene BoCP3 and aspartic protease gene BoLSC807 suggested the role of H2S in alleviating protein degradation during broccoli senescence. H2S up-regulated the expression of sulfur metabolism genes BoSR and BoOASTL, and the antioxidant gene BoCAT. These results show that H2S plays a vital role in alleviating broccoli senescence through a broad regulation on gene expression of reactive oxygen species (ROS) metabolism genes, ethylene synthesis genes, and protease genes.
Highlights
Broccoli (Brassica oleracea var. italica) is an important vegetable crop rich in vitamins and sulforaphane
Production of ethylene plays an important role in regulating the yellowing of florets after harvest, because chlorophyll loss is associated with an increase in ethylene synthesis in florets (Tian et al, 1994)
We determined the effect of H2S fumigation on Chl degradation, which is the principle symptom of broccoli senescence
Summary
Broccoli (Brassica oleracea var. italica) is an important vegetable crop rich in vitamins and sulforaphane. H2S up-regulated the expression of sulfur metabolism genes BoSR and BoOASTL, and the antioxidant gene BoCAT These results show that H2S plays a vital role in alleviating broccoli senescence through a broad regulation on gene expression of reactive oxygen species (ROS) metabolism genes, ethylene synthesis genes, and protease genes. Postharvest broccoli florets experience senescence similar to those seen in developmental leaf senescence at biochemical and transcriptional levels, involving decline in photosynthesis and degradation of macromolecules such as proteins, lipids, and chlorophyll (Buchanan-Wollaston, 1997; Smart, 1994). In this article we investigate accelerated senescence of broccoli florets in darkness using biochemical and molecular analysis and the interplay of H2S with sulfur metabolism, the ethylene pathway, and protein degradation
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