The present study is focused on protein degradation during astaxanthin synthesis in Haematococcus plu- vialis under high irradiance and nitrogen deficient conditions. It was found that with the onset of astaxanthin sy...The present study is focused on protein degradation during astaxanthin synthesis in Haematococcus plu- vialis under high irradiance and nitrogen deficient conditions. It was found that with the onset of astaxanthin synthesis in the cultures of high light and nitrogen-free （HF）, high light and nitrogen-repletion （HR）, and low light and nitrogen-free （LF）, （1） endopeptidase （EP） activities increased along with decrease in protein content, （2） asparagine in HF and HR rose significantly before the first 4 and 5 day, but fell after that time. While, it increased slowly and continuously in LF, （3） ammonium increased continuously in HF and HR, whereas in LF, it was detected on the sixth day, and increased slowly on the following days. By contrast, in low light and nitrogen-repletion culture, （LR）, the contents of protein and asparagine as well as EP activity were maintained relatively constant, no astaxanthin and ammonium were detected. Furthermore, when HF was sealed and bubbled with CO2-free gas （02 and N2）, astaxan- thin content increased as the protein level decreased. These results strongly suggest that （1） the degraded protein served as a substitutive carbon source, to some extent, for the biosynthesis of astaxanthin, （2） endopeptidase was involved in the degradative process, （3） for detoxification, part of the ammonium generated by protein degradation was transiently stored in asparagine, whereas the rest of it was expelled into the culture broth.展开更多
Aims Populus deltoides and P.euramericana are widely used in China as major forestry species.At present,little is known about their responses to nitrogen(N)deficiency when grown in monocultures or mixed plantations.Th...Aims Populus deltoides and P.euramericana are widely used in China as major forestry species.At present,little is known about their responses to nitrogen(N)deficiency when grown in monocultures or mixed plantations.The aim of this investigation was to analyze the growth,and morphological and physiological responses of P.deltoides and P.euramericana to different N levels under competition conditions.Methods We employed two Populus species(P.deltoides and P.euramericana)to discover how N deficiency affects plant traits under different competition types(P.deltoides×P.deltoides,intraspecific competition;P.euramericana×P.euramericana,intraspecific competition;P.deltoides×P.euramericana,interspecific competition).Potted seedlings were exposed to two N levels(normal N,N deficiency),and nitrogen-and competition-driven differences in growth,morphology and physiology were examined.Important Findings Under normal N conditions,interspecific competition significantly decreased the total root weight,root mass fraction(RMF),root–shoot ratio(R/S)and carbon/nitrogen ratio(C/N),and increased the leaf dry weight,leaf mass fraction and total leaf area of P.euramericana compared with intraspecific competition.The same conditions significantly affected the growth and morphological variables of P.deltoides,except for the dry weight of fine roots,R/S,specific leaf area,RMF,total nitrogen content and C/N compared with intraspecific competition.In addition,chlorophyll a(Chla),total chlorophyll(Tchl),carotenoid contents(Caro)and the carbon isotope composition(δ13C)of P.deltoides were significantly lower in interspecific competition than in intraspecific competition,but no difference was detected in P.euramericana.The effects of N deficiency on P.deltoides under intraspecific competition were stronger than under interspecific competition.In contrast,the effects of N deficiency on P.euramericana between intraspecific and interspecific competition were not significantly different.These results suggest that under normal N condition,P.deltoides is expected to gain an advantage in monocultures rather than in mixtures with P.euramericana.Under N deficiency,the growth performance of P.euramericana was more stable than that of P.deltoides under both cultivation modes.展开更多
基金Supported by the National Natural Science Foundation of China (No.20536040)the Natural Project of Key Fundamental Research (2003CB716003, 2007CB707802).
文摘The present study is focused on protein degradation during astaxanthin synthesis in Haematococcus plu- vialis under high irradiance and nitrogen deficient conditions. It was found that with the onset of astaxanthin synthesis in the cultures of high light and nitrogen-free （HF）, high light and nitrogen-repletion （HR）, and low light and nitrogen-free （LF）, （1） endopeptidase （EP） activities increased along with decrease in protein content, （2） asparagine in HF and HR rose significantly before the first 4 and 5 day, but fell after that time. While, it increased slowly and continuously in LF, （3） ammonium increased continuously in HF and HR, whereas in LF, it was detected on the sixth day, and increased slowly on the following days. By contrast, in low light and nitrogen-repletion culture, （LR）, the contents of protein and asparagine as well as EP activity were maintained relatively constant, no astaxanthin and ammonium were detected. Furthermore, when HF was sealed and bubbled with CO2-free gas （02 and N2）, astaxan- thin content increased as the protein level decreased. These results strongly suggest that （1） the degraded protein served as a substitutive carbon source, to some extent, for the biosynthesis of astaxanthin, （2） endopeptidase was involved in the degradative process, （3） for detoxification, part of the ammonium generated by protein degradation was transiently stored in asparagine, whereas the rest of it was expelled into the culture broth.
基金supported by the Key laboratory project of the Ecological Security and Protection Key Laboratory of Sichuan Province(ESP201501)the Talent Program of the Hangzhou Normal University(2016QDL020).
文摘Aims Populus deltoides and P.euramericana are widely used in China as major forestry species.At present,little is known about their responses to nitrogen(N)deficiency when grown in monocultures or mixed plantations.The aim of this investigation was to analyze the growth,and morphological and physiological responses of P.deltoides and P.euramericana to different N levels under competition conditions.Methods We employed two Populus species(P.deltoides and P.euramericana)to discover how N deficiency affects plant traits under different competition types(P.deltoides×P.deltoides,intraspecific competition;P.euramericana×P.euramericana,intraspecific competition;P.deltoides×P.euramericana,interspecific competition).Potted seedlings were exposed to two N levels(normal N,N deficiency),and nitrogen-and competition-driven differences in growth,morphology and physiology were examined.Important Findings Under normal N conditions,interspecific competition significantly decreased the total root weight,root mass fraction(RMF),root–shoot ratio(R/S)and carbon/nitrogen ratio(C/N),and increased the leaf dry weight,leaf mass fraction and total leaf area of P.euramericana compared with intraspecific competition.The same conditions significantly affected the growth and morphological variables of P.deltoides,except for the dry weight of fine roots,R/S,specific leaf area,RMF,total nitrogen content and C/N compared with intraspecific competition.In addition,chlorophyll a(Chla),total chlorophyll(Tchl),carotenoid contents(Caro)and the carbon isotope composition(δ13C)of P.deltoides were significantly lower in interspecific competition than in intraspecific competition,but no difference was detected in P.euramericana.The effects of N deficiency on P.deltoides under intraspecific competition were stronger than under interspecific competition.In contrast,the effects of N deficiency on P.euramericana between intraspecific and interspecific competition were not significantly different.These results suggest that under normal N condition,P.deltoides is expected to gain an advantage in monocultures rather than in mixtures with P.euramericana.Under N deficiency,the growth performance of P.euramericana was more stable than that of P.deltoides under both cultivation modes.
