Transcriptome profiling reveals the roles of pigment mechanisms in postharvest broccoli yellowing

Postharvest broccoli is prone to yellowing during storage,which is the key factor leading to a reduction in value.To explore appropriate control methods,it is important to understand the mechanisms of yellowing.We analyzed the genes related to the metabolism of chlorophyll,carotenoids,and flavonoids and the transcription factors(TFs)involved in broccoli yellowing using transcriptome sequencing profiling.Broccoli stored at 10℃showed slight yellowing on postharvest day 5 and serious symptoms on day 12.There were significant changes in chlorophyll fluorescence kinetics,mainly manifesting as a decrease in the Fv/Fm value and an increase in nonphotochemical quenching,during the yellowing process.Transcriptome sequencing profiles from samples of fresh broccoli and broccoli with slight and severe yellowing revealed 6,5,and 4 differentially expressed genes involved in chlorophyll metabolism,carotenoid biosynthesis,and flavonoid biosynthesis,respectively.The transcription factor gene ontology categories showed that the MYB,bHLH,and bZip gene families were involved in chlorophyll metabolism.In addition,the transcription factor families included NACs and ethylene response factors(ERFs)that regulated carotenoid biosynthesis.Reverse transcription polymerase chain reaction further confirmed that bHLH66,PIF4,LOB13,NAC92,and APL were vital transcription factors that potentially regulated the CAO and HYD genes and were involved in chlorophyll metabolism and the carotenoid biosynthetic process.The flavonoid biosynthetic pathway was mainly regulated by MYBs,NACs,WRKYs,MADSs,and bZips.The results of the differentially expressed gene(DEG)and pigment content analyses indicated that the transcriptome data were accurately and positively associated with broccoli yellowing.

PuMYB21/PuMYB54 coordinate to activate PuPLDβ1 transcription during peel browning of cold-stored“Nanguo”pears

Refrigeration is commonly used to extend the storage life of“Nanguo”pears,but fruit in long-term refrigeration is prone to peel browning,which is related to membrane lipid degradation.To determine the mechanism of membrane lipid degradation,we identified two R2R3-MYB transcription factors(TFs),PuMYB21 and PuMYB54,from“Nanguo”pears,which were notably expressed in response to cold stress and during the peel-browning process.The results from yeast one-hybrid,electrophoretic mobility shift,and transient expression assays indicated that both PuMYB21 and PuMYB54 directly bind to the promoter of PuPLDβ1(a key enzyme catalyzing the hydrolysis of membrane phospholipids)and activate its expression,which probably enhances the degradation of membrane phospholipids and eventually results in peel browning.Moreover,the overexpression of PuMYB21 and PuMYB54 can greatly activate the transcription of endogenous PuPLDβ1 in both“Nanguo”pear fruits and calli,and their silencing can inhibit its transcription.Furthermore,yeast two-hybrid,bimolecular fluorescence complementation,and pull-down assays verified that PuMYB21 interacts with PuMYB54 to enhance the expression of PuPLDβ1.In summary,we demonstrate that PuMYB21 and PuMYB54 may have roles in membrane lipid metabolism by directly binding to the downstream structural gene PuPLDβ1 during the low temperature-induced peel browning of“Nanguo”pears.

Characteristics of life-cycle carbon dioxide emissions of arterial highway maintenance and the influencing factors

With the focus of highway development transitioning from construction to maintenance,a comprehensive understanding of the characteristics and influencing factors of carbon dioxide(CO_(2))emissions from highway maintenance activities is crucial for formulating effective strategies to promote the low-carbon development of road infrastructure.However,the quantitative relationships between CO_(2) emissions from highway maintenance schemes and factors such as pavement deterioration,traffic volume,and road grade remain unclear owing to a lack of compre-hensive,multi-category,and real data.Using real maintenance data from 340 arterial highway segments in China,this study conducts the life cycle assessment(LCA)to estimate CO_(2) emissions from maintenance activities and examines the primary emission sources among various structural layers and materials.Furthermore,multiple linear regression(MLR)analysis is conducted to investigate the impact of traffic volume,road grade,and pavement deterioration on CO_(2) emissions from maintenance projects,and factors influencing the early-stage degradation of pavement performance.The results demonstrate that average CO_(2) emissions from heavy rehabilitation projects are 6.97 times higher than those from medium rehabilitation projects.Emissions from heavy rehabilitation projects exhibit a significantly negative linear relationship with the riding quality index(RQI)before maintenance(p<0.05),and emissions from medium rehabilitation projects show a significant negative linear relationship with the pavement condition index(PCI)before maintenance(p<0.05).Emissions from heavy and medium rehabilitation projects are significantly positively correlated with heavy vehicle traffic volume before maintenance(p<0.05).Moreover,the early-stage degradation of PCI after heavy rehabilitation and RQI after medium rehabilitation exhibit significantly negative linear relationships with their respective in-dicators before maintenance(p<0.05).The early-stage degradation of RQI after heavy rehabilitation is significantly positively correlated with CO_(2) emissions from the base course and cushion layers(p<0.05).The findings emphasize that timely maintenance and reduction of CO_(2) emissions from asphalt mixing equipment are essential for mitigating emissions from road maintenance.This study offers valuable insights for advancing the low-carbon development of highways in temperate regions.

The membrane lipid metabolism in horticultural products suffering chilling injury

Horticultural commodities suffer chilling injury following exposure to extremely low temperatures,which results in visible symptoms and considerable quality loss.Therefore,it is of significance to understand the mechanism of this physiological disorder and to develop effective strategies to control it.Chilling stress causes alteration in structure and function of the plasma membrane,which is assumed to be the primary event in response to cold stress.During this process,the membrane lipid metabolism plays a pivotal role in membrane fluidity and stability.In this review,we summarized the possible roles of membrane lipid metabolism in the development of chilling injury,having the potential for developing effective strategies to alleviate chilling injury in horticultural products under refrigerated storage in practice.