Gel stained with Coomassie brilliant blue (cbb) shows the RuBisCO large sub-unit (RBCL) and the decline of this major protein indicated that proteolysis and N remobilization are induced
Gel stained with Coomassie brilliant blue (cbb) shows the RuBisCO large sub-unit (RBCL) and the decline of this major protein indicated that proteolysis and N remobilization are induced. provokes the induction of senescence and several cysteine and serine protease activities. The study of protease activities during the senescence of cotyledons seems to be a promising experimental model to investigate the regulation and genotypic variability of proteolysis associated with efficient N remobilization. L., protease activity, senescence, cotyledon, nitrogen remobilization efficiency, phytohormones, genotypic variability 1. Introduction Oilseed rape (L.) is the second largest oleaginous crop worldwide behind soybean with a world production attaining about 64 million tonnes of grain [1] and the production of oilseed rape is usually experiencing a resurgence of interest thanks to the development of many food processing, green chemistry, and industrial markets based on biosourced products. However, despite a strong need for N fertilizers [2], oilseed rape is usually characterized by a weak N use efficiency with only 50% of N from fertilizers being recovered in seeds [3]. This low N use efficiency is mainly related to a low N remobilization efficiency during the sequential leaf senescence that occurs during the vegetative stages and the transition between vegetative and reproductive phases of development [4,5,6,7,8,9]. Considering that the improvement of N remobilization efficiency is usually a major lever to optimize the agri-environmental performance of oilseed rape, it is necessary to understand the N remobilization associated with senescence [7,8,9,10]. Senescence is usually a genetically controlled process involving many physiological, biochemical, and molecular events, resulting in a strong degradation of macromolecules as nucleic acids, lipids, and proteins, and leading to the death of all or part of the herb [7,11,12]. Sequential senescence, affecting older leaves along the axis of the herb, leads to nutrient remobilization from source leaves to the sink organs such as young leaves [7]. This process is not only a degenerative process, but is an essential process for the survival of the rest of the herb and the survival of the species seed production [13]. Moreover, senescence is usually a process specifically linked to seed yield and herb productivity [14,15,16]. The senescence process is usually tightly controlled by environmental and endogenous factors [17,18]. Among the endogenous factors, many hormonal pathways are involved in the unfavorable or positive regulation of leaf senescence. These pathways play a role at all stages of senescence, whether they be the initiation, progression, or final stage of senescence [18,19,20,21,22,23]. Cytokinins (CKs), gibberellins (GAs), and auxin (IAA) are hormones involved in the negative regulation of senescence [20,24,25,26,27]. In contrast, abscisic acid (ABA), salicylic acid (SA), ethylene (ET), methyl jasmonate (MeJA), brassinosteroids (BR), and strigolactones (SL) have the capacity to positively regulate senescence [18,19,20,21,23]. During senescence, protein degradation represents the most important Belizatinib degradation process and N remobilization efficiency improvement in oilseed rape is usually tightly associated with the optimization of proteolysis during leaf senescence [8,9,28,29]. Recent work has focused on the understanding of proteolysis processes during the senescence of oilseed rape to improve the N remobilization efficiency [7,9,29]. During leaf senescence, protein breakdown is related to many protease classes: aspartic proteases, metalloproteases, serine proteases (SPs), cysteine proteases (CPs), and the proteasome [30]. Among these classes, CPs and SPs are the most strongly associated with leaf senescence in various species [30,31,32,33,34]. Furthermore, in oilseed rape, recent studies have shown that this genotypic variability of leaf N remobilization efficiency under N limitation is related to the proteolysis efficiency and specific protease activities [8,9]. For instance, under low N conditions, the genotype Tnor characterized by a high N remobilization efficiency was able to maintain its leaf biomass production thanks to higher soluble protein degradation and N remobilization, contrary to the genotype.(2000) [59] demonstrated that a defect in the synthesis of SA in delayed senescence and repressed the gene expression of (encoding a cysteine protease). in senescing cotyledons. The infiltration of ABA and SA provokes the induction of senescence and several cysteine and serine protease activities. The study of protease activities during the senescence of cotyledons seems to be a promising experimental model to investigate the regulation and genotypic variability of proteolysis associated with efficient N remobilization. L., protease activity, senescence, cotyledon, nitrogen remobilization efficiency, phytohormones, genotypic variability 1. Introduction Oilseed rape (L.) is the second largest oleaginous crop worldwide behind soybean with a world production attaining about 64 million tonnes of grain [1] and the production of oilseed rape is usually experiencing a resurgence of interest thanks to the development of many food processing, green chemistry, and industrial markets based on biosourced products. However, despite a strong need for N fertilizers [2], oilseed rape is usually characterized by a weak N use efficiency with only 50% of N from fertilizers being recovered in seeds [3]. This low N use efficiency is mainly related to a low N remobilization efficiency during the sequential leaf senescence that occurs during the vegetative stages and the transition between vegetative and reproductive phases of development [4,5,6,7,8,9]. Considering that the improvement of N remobilization efficiency is usually a major lever to optimize the agri-environmental performance of oilseed rape, it is necessary to understand the N remobilization associated with senescence [7,8,9,10]. Senescence is usually a genetically controlled process involving many physiological, biochemical, and molecular events, resulting in a strong degradation of macromolecules as nucleic acids, lipids, and proteins, and leading to the death of all or part of the herb [7,11,12]. Sequential senescence, affecting older leaves along the axis of the herb, leads to nutrient remobilization from source leaves to the sink organs such as young leaves [7]. This process is not only a degenerative process, but is an essential process for the survival of the rest of the herb and the survival of the species seed production [13]. Moreover, senescence is usually a process specifically linked to seed yield and herb productivity [14,15,16]. The senescence process is usually tightly controlled by environmental and endogenous factors [17,18]. Among the endogenous factors, many hormonal pathways are involved in the unfavorable or positive regulation of leaf senescence. These pathways play a role at all stages of senescence, whether they be the initiation, progression, or final stage of senescence [18,19,20,21,22,23]. Cytokinins (CKs), gibberellins (GAs), and auxin (IAA) are hormones involved in the negative regulation of senescence [20,24,25,26,27]. In contrast, abscisic acid (ABA), salicylic acid (SA), ethylene (ET), methyl jasmonate (MeJA), brassinosteroids (BR), and strigolactones (SL) have the capacity to positively regulate senescence [18,19,20,21,23]. During senescence, protein degradation represents the most important degradation process and N remobilization efficiency improvement in oilseed rape is usually tightly associated with the optimization of proteolysis during leaf senescence [8,9,28,29]. Recent work has focused on the understanding of proteolysis processes during the senescence of oilseed rape to improve the N remobilization efficiency [7,9,29]. During leaf senescence, protein breakdown is related to many protease classes: aspartic proteases, metalloproteases, serine proteases (SPs), cysteine proteases (CPs), and the proteasome [30]. Among these classes, CPs and SPs are the most strongly associated with leaf senescence INCENP in various species [30,31,32,33,34]. Furthermore, in oilseed rape, recent studies have shown that the genotypic variability of leaf N remobilization efficiency under N limitation is related to the proteolysis efficiency and specific protease activities [8,9]. For instance, under low N conditions, the genotype Tnor characterized by a high N remobilization efficiency was able to maintain its leaf biomass production thanks to higher soluble protein degradation and N remobilization, contrary to the genotype Samoura?, which is characterized by a low N remobilization efficiency [8]. This higher leaf proteolysis of Tnor compared with Samoura? was correlated with an increase in SP and CP activities and Belizatinib with the appearance of new CP activities (RD21-like, RD19-like, SAG12-like, cathepsin-B, XBCP3-like, and Aleurain-like proteases) [35]. Additionally, compared with Samoura?, the genotype Tnor was characterized by a higher hormonal ratio ([SA] + [ABA])/([CK]) during leaf Belizatinib senescence that was induced by nitrate limitation. These changes in the ([SA] + [ABA])/([CK]) ratios are also associated with a higher proteolysis and the increase or the induction of protease activities [35]. Based on these previous results and on the fact that cotyledons are also subjected to a senescence process, it could be assumed that the contrasting protease activities observed during leaf senescence at the vegetative stages between.