| Huangjinya is a typical yellowing tea tree variety,which has the characteristics of light sensitivity,low chlorophyll content in yellowed leaves.The main hindered site of chlorophyll synthesis is faecal Coproporphyrinogen Ⅲ→Protoporphyrinogen Ⅸ→Protoporphyrin IX,and the reaction is catalyed by Coproporphyrinogen oxidase(CPOX)and Protoporphyrinogen oxidase(Protox/PPOX).The expression of CsCPOX and CsPPOX genes and the activitives of CPOX and PPOX enzymes play key regulatory roles in yellowing of Huangjinya leaves.In this study,the leaves of 4-year-old Huangjinya were used as experimental materials with different light and different leaf positions treatments.Performing gene expression analysis,combining leaf PPOX and PPOX activities,leaf color difference analysis and pigment content detection under different treatments,preliminary verification of the regulatory effect of CsCPOX and CsPPOX on leaf yellowing.This provides a theoretical basis for the yellowing mechanism of leaf color of Huangjinya.The results were as below1.Two CsCPOX sequences were cloned from Camellia sinensis var.Huangjingya,and named CsCPOXl and CsCPOX2.The open reading frames were 1224bp and 1317bp,encoding 407 and 438 amino acids,espectively.CsCPOX had the conserved domains Coprogen oxidas,which had the functions of CPOX.The relative molecular masses of CsCPOX proteins were predicted to be 45.76kD and 49.53kD.The theoretical isoelectric points of CsCPOXl and CsCPOX2 were 6.05 and 6.51.CsCPOXl and CsCPOX2 were acidic protein,subcellular localizations were on the chloroplast.CsCPOXl has the closest relationship with PaCPOX and PvCPOX,with 88.12%and 87.46%homology.CsCPOX2 was closest to NsCPOX with 80.00%homology.CsCPOX was not obviously controlled by light intensity and the regulation of CsCPOX gene was also affected by other factors2.Two CsPPOX sequences were cloned from Camellia sinensis var.Huangjingya,named CsPPOXl and CsPPOX2.The open reading frames were 1623bp and 1368bp,encoding 540 and 455 amino acids.CsPPOX had the conserved domains PLN02576,proto IX ox,and Amino oxidase,which had the functions of PPOX.The relative molecular masses of CsPPOX proteins were predicted to be 58.99kD and 50.29kD.The theoretical isoelectric points of CsCPOXl and CsCPOX2 were 9.43 and 5.82.CsPPOX1 was basic protein,and subcellular localization was on the mitochondria.CsPPOX2 was acidic proteins and localized on the chloroplast.CsPPOXl and CsPPOX2 were closest to VvPPOX and RcPPOX,with homology of 82.05%and 64.97%.CsPPOX was significantly regulated by light intensity CsPPOX expression was positively correlated with light and positively correlated with leaf position and significantly negative correlated with chlorophyll content.It was inversely related to the degree of yellowing of Huangjinya.3.CPOX and PPOX could affect the yellowing of the color of Huangjinya,the blocked chlorophyll synthesis pathway may be the main way to affect the yellowing of Huangjinya.Under shading conditions,the content of chlorophyll,flavonoids,and carotene decreased,and the activities of CPOX and PPOX activities increased.The expression of the two genes was controlled by light,and the down-regulation of CsPPOXl under strong light was the main reason for the inhibition of chlorophyll synthesis in Huangjinya.However,the molecular mechanism that light intensity regulated the expression of CsPPOX1 and CsCPOX was unclear,and further research was needed. |
