The role of ANAC072 in the regulation of chlorophyll degradation during age- and dark-induced leaf senescence

Abstract

ANAC072 positively regulates both age- and dark-induced leaf senescence through activating the transcription of NYE1. Leaf senescence is integral to plant development, which is age-dependent and strictly regulated by internal and environmental signals. Although a number of senescence-related mutants and senescence-associated genes (SAGs) have been identified and characterized in the past decades, the general regulatory network of leaf senescence is still far from being elucidated. Here, we report the role of ANAC072, an SAG identified through bioinformatics analysis, in the regulation of chlorophyll degradation during natural and dark-induced leaf senescence. The expression of ANAC072 was increased with advancing leaf senescence in Arabidopsis. Leaf degreening was significantly delayed under normal or dark-induced conditions in anac072-1, a knockout mutant of ANAC072, with a higher chlorophyll level detected. In contrast, an overexpression mutant, anac072-2, with ANAC072 transcription markedly upregulated, showed an early leaf-yellowing phenotype. Consistently, senescent leaves of the loss-of-function mutant anac072-1 exhibited delays in the decrease of photosynthesis efficiency of photosystem II (F v/F m ratio) and the increase of plasma membrane ion leakage rate as compared with corresponding leaves of wild-type Col-0 plants, whereas the overexpression mutant anac072-2 showed opposite changes. Our data suggest that ANAC072 plays a positive role during natural and dark-induced leaf senescence. In addition, the transcript level of NYE1, a key regulatory gene in chlorophyll degradation, relied on the function of ANAC072. Combining these analyses with electrophoretic mobility shift assay and chromatin immunoprecipitation, we demonstrated that ANAC072 directly bound to the NYE1 promoter in vitro and in vivo, so ANAC072 may promote chlorophyll degradation by directly upregulating the expression of NYE1.

Transcription factor RD26 is a key regulator of metabolic reprogramming during dark‐induced senescence

“…RD26 shows enhanced expression during senescence and it triggers developmental and dark‐induced senescence when overexpressed under the control of the constitutive Cauliflower Mosaic Virus (CaMV) 35S promoter (hereafter, RD26Ox ), while senescence is delayed in two rd26 knockout mutants ( rd26‐1 and rd26‐2 ; see Materials and Methods) (Balazadeh et al ., ; Li et al ., ; Figs S1, S2). Here, we sought to identify the gene regulatory network (GRN) that this TF controls.…”

“…RD26, a member of the ATAF subfamily of TFs in A. thaliana (Jensen et al ., ), has previously been identified as a positive regulator of developmental and dark‐induced senescence (Li et al ., ) and jasmonic acid‐induced Chl degradation (Zhu et al ., ), while it is also involved in abiotic and biotic stress signaling (Fujita et al ., ; Tran et al ., ; Zheng et al ., ; Ye et al ., ). Here, we report RD26 as an important regulator of metabolic reprogramming during senescence by controlling the expression of genes across the entire spectrum of the cellular degradation hierarchy.…”

BrWRKY65, a WRKY Transcription Factor, Is Involved in Regulating Three Leaf Senescence-Associated Genes in Chinese Flowering Cabbage

“…Consistent with its trend in our RNA-seq database, BrWRKY65 transcript level increased during senescence, reaching about 4.2- and 3.8-fold of the initial level at day seven and nine, respectively (Figure 4). In addition, as leaf yellowing is due to chlorophyll degradation [29,32,40,41,42,43], and dark-inducible ( DIN ) genes are induced in dark-adapted and senescing leaves [44,45], which have been used previously as markers to characterize senescence-associated responses. Therefore, we further searched the SAG genes in our RNA-seq transcriptome database, and three SAG s such as BrNYC1 (NON-YELLOW COLORING1/Chl b reductase) (XP_009139641.1) and BrSGR1 (STAY-GREEN1) (XP_018512704.1) associated with chlorophyll degradation, and BrDIN1 (XP_009150416.1) were selected.…”

“…Accordingly, whether BrWRKY65 and BrWRKY75 act together or individually to regulate SAGs is an interesting research issue in the future. Moreover, it has been reported other types of Arabidopsis TFs, such as ABSCISIC ACID INSENSITIVE3 (ABI3) [47], ABI5, ENHANCED EM LEVEL (EEL) [48], phytochrome-interacting factor 4 (PIF4) [49], MYC2/3/4 [50], ANAC072 [43], and ERF [51], are reported to activate genes related to chlorophyll degradation such as NYE1 (also known as SGR1 ), NYC1 , and PAO (pheophorbide a oxygenase) via directly binding to their promoters, leading to accelerated chlorophyll degradation during leaf senescence, seed or fruit degreening. Intriguingly, Arabidopsis ETHYLENE INSENSITIVE3 (EIN3) and ORE1/NAC2 establish a network controlling ethylene-induced leaf senescence via directly targeting NYE1 , NYC1 , and PAO [52].…”

Functional and RNA-Sequencing Analysis Revealed Expression of a Novel Stay-Green Gene from Zoysia japonica (ZjSGR) Caused Chlorophyll Degradation and Accelerated Senescence in Arabidopsis

“…NAC TFs have been reported to function efficiently in chlorophyll degradation and leaf senescence, and actively participant in ABA, MeJA, and ethylene signaling which could act back on leaf senescence (Bu et al, 2008; Yang et al, 2011; Kim et al, 2014; Sakuraba et al, 2015; Takasaki et al, 2015; Li et al, 2016). Take the significantly up-regulated AtNAC92 as an example in our study, it was reported to work together with other NAC domain proteins to regulate the expression of many genes in senescence (Balazadeh et al, 2010; Breeze and Buchanan-Wollaston, 2011).…”