CmoNAC1 in pumpkin rootstocks improves salt tolerance of grafted cucumbers by binding to the promoters of CmoRBOHD1, CmoNCED6, CmoAKT1;2 and CmoHKT1;1 to regulate H_(2)O_(2), ABA signaling and K^(+)/Na^(+) homeostasis

The NAC transcription factor is a type of plant-specific transcription factor that can regulate plant salt tolerance,but the underlying mechanism is unclear in grafted vegetables.H2O2 and ABA in pumpkin rootstocks can be transported to cucumber scion leaves,promoting stomatal closure to improve salt tolerance of grafted cucumbers.Despite these observations,the regulatory mechanism is unknown.Here,our research revealed that CmoNAC1 is a key transcription factor that regulates H_(2)O_(2) and ABA signaling in pumpkin roots under salt stress.The function of CmoNAC1 was analyzed using root transformation and RNA-seq,and we found that pumpkin CmoNAC1 promoted the production of H_(2)O_(2) and ABA via CmoRBOHD1 and CmoNCED6,respectively,and regulated K^(+)/Na^(+) homeostasis via CmoAKT1;2,CmoHKT1;1,and CmoSOS1 to improve salt tolerance of grafted cucumbers.Root knockout of CmoNAC1 resulted in a significant decrease in H_(2)O_(2)(52.9%and 32.1%)and ABA(21.8%and 42.7%)content and K^(+)/Na^(+) ratio(81.5%and 56.3%)in leaf and roots of grafted cucumber,respectively,while overexpression showed the opposite effect.The root transformation experiment showed that CmoNCED6 could improve salt tolerance of grafted cucumbers by regulating ABA production and K^(+)/Na^(+) homeostasis under salt stress.Finally,we found that CmoNAC1 bound to the promoters of CmoRBOHD1,CmoNCED6,CmoAKT1;2,and CmoHKT1;1 using yeast one-hybrid,luciferase,and electrophoretic mobility shift assays.In conclusion,pumpkin CmoNAC1 not only binds to the promoters of CmoRBOHD1 and CmoNCED6 to regulate the production of H_(2)O_(2) and ABA signals in roots,but also binds to the promoters of CmoAKT1;2 and CmoHKT1;1 to increase the K^(+)/Na^(+) ratio,thus improving salt tolerance of grafted cucumbers.

Insulin peptides and their receptors regulate ovarian development and oviposition behavior in Diaphorina citri

Diaphorina citri is an important vector of Citrus Huanglongbing(HLB)disease.After feeding on young host plant shoots,the population of D.citri can increase significantly.Females also only lay eggs on young shoots.However,there are few studies on the mechanism of this phenomenon.Exogenous nutrient signals can affect the insulin signaling system of D.citri after feeding on young shoots.In this study,the expression of upstreamfactors DclLPl,DclLP2,and DclR in the insulin signaling system of D.citri was upregulated after feeding on young shoots.After being silenced by RNA interference technology,the results showed that the number of oviposited eggs of D.citri was significantly decreased and the ovarian development was inhibited with severe vacuolation.In addition,detection using quantitative reverse transcription-polymerase chain reaction showed that the upstream regulatory gene DcRheb of the target of rapamycin(TOR)pathway and the downstream reproduction-related DcVg gene were also significantly downregulated.These results suggest that feeding upon young shoots may upregulate the expression levels of upstream factors DclLPl,DclLP2,and DclR in the insulin signaling system.The signal will be through upregulating the expression of DcRheb,an upstream gene of the TOR signaling pathway.This in turn influences yolk metabolism,which eventually causes the ovaries of female D.citri to mature and therefore initiate oviposition behavior.