Multiomics analyses unveil the involvement of microRNAs in pear fruit senescence under high-or low-temperature conditions

Senescence leads to declines in fruit quality and shortening of shelf life.It is known that low temperatures(LTs)efficiently delay fruit senescence and that high temperatures(HTs)accelerate senescence.However,the molecular mechanism by which temperature affects senescence is unclear.Herein,through multiomics analyses of fruits subjected to postharvest HT,LT,and room temperature treatments,a total of 56 metabolic compounds and 700 mRNAs were identified to be associated with fruit senescence under HT or LT conditions.These compounds could be divided into antisenescent(I→III)and prosenescent(IV→VI)types.HT affected the expression of 202 mRNAs to enhance the biosynthesis of prosenescent compounds of types V and VI and to inhibit the accumulation of antisenescent compounds of types II and III.LT affected the expression of 530 mRNAs to promote the accumulation of antisenescent compounds of types I and II and to impede the biosynthesis of prosenescent compounds of types IV and V.Moreover,16 microRNAs were isolated in response to HT or LT conditions and interacted with the mRNAs associated with fruit senescence under HT or LT conditions.Transient transformation of pear fruit showed that one of these microRNAs,Novel_188,can mediate fruit senescence by interacting with its target Pbr027651.1.Thus,both HT and LT conditions can affect fruit senescence by affecting microRNA–mRNA interactions,but the molecular networks are different in pear fruit.

The NAM/ATAF1/2/CUC2 transcription factor PpNAC.A59 enhances PpERF.A16 expression to promote ethylene biosynthesis during peach fruit ripening

Peach is a typical climacteric fruit that releases ethylene during fruit ripening.Several studies have been conducted on the transcriptional regulation of ethylene biosynthesis in peach fruit.Herein,an ethylene response factor,PpERF.A16,which was induced by exogenous ethylene,could enhance ethylene biosynthesis by directly inducing the expression of 1-aminocyclopropane-1-carboxylic acid synthase(PpACS1)and 1-aminocyclopropane-1-carboxylic acid oxidase(PpACO1)genes.Moreover,the NAM/ATAF1/2/CUC2(NAC)transcription factor(TF)PpNAC.A59 was coexpressed with PpERF.A16 in all tested peach cultivars.Interestingly,PpNAC.A59 can directly interact with the promoter of PpERF.A16 to induce its expression but not enhance LUC activity driven by any promoter of PpACS1 or PpACO1.Thus,PpNAC.A59 can indirectly mediate ethylene biosynthesis via the NAC-ERF signaling cascade to induce the expression of both PpACS1 and PpACO1.These results enrich the genetic network of fruit ripening in peach and provide new insight into the ripening mechanism of other perennial fruits.