Genetic Interaction Among Phytochrome, Ethylene and Abscisic Acid Signaling During Dark-Induced Senescence in Arabidopsis thaliana

Abstract

Leaf senescence is induced by various internal and external stimuli. Dark-induced senescence has been extensively investigated, but the detailed mechanism underlying it is not well understood. The red light/far-red light receptor phytochrome B and its downstream transcription factors, PYHTOCHROME INTERACTING FACTORs (PIFs) 4 and 5, are known to play an important role in dark-induced senescence. Furthermore, the senescence-inducing phytohormones, ethylene and abscisic acid (ABA) are reported to be involved in dark-induced senescence. In this study, we analyzed the relationship between ethylene, ABA and PIFs in dark-induced leaf senescence. A triple mutant of the core ABA signaling components; SNF1-related protein kinases 2D (SRK2D), SRK2E, and SRK2I, displayed an ABA insensitive phenotype in ABAinduced senescence, whilst the ethylene insensitive mutant ein2 demonstrated low sensitivity to ABA, suggesting that ethylene signaling is involved in ABA-induced senescence. However, the pif4 pif5 mutant did not display low sensitivity to ABA, suggesting that PIF4 and PIF5 act upstream of ABA signaling. Although PIF4 and PIF5 reportedly regulate ethylene production, the triple mutant ein2 pif4 pif5 showed a stronger delayed senescence phenotype than ein2 or pif4 pif5, suggesting that EIN2 and PIF4/PIF5 partially regulate leaf senescence independently of each other. While direct target genes for PIF4 and PIF5, such as LONG HYPOCOTYL IN FAR-RED1 (HFR1) and PHYTOCHROME INTERACTING FACTOR 3-LIKE 1 (PIL1), showed transient upregulation under dark conditions (as is seen in the shade avoidance response), expression of STAY GREEN1 (SGR1), ORESARA1 (ORE1) and other direct target genes of PIF5, continued to increase during dark incubation. It is possible that transcription factors other than PIF4 and PIF5 are involved in the upregulation of SGR1 and ORE1 at a later stage of dark-induced senescence. Possible candidates are senescenceinduced senescence regulators (SIRs), which include the NAC transcription factors ORE1 and AtNAP. In fact, ORE1 is known to bind to the SGR1 promoter and promotes its expression. It is therefore inferred that the phytochrome-PIF pathway regulates initial activation of senescence and subsequently, induced SIRs reinforce leaf senescence during dark-induced senescence.

MicroRNA775 and targetGalactosyltransferase(GALT9) module regulates recovery from submergence induced senescence by modulatingSAGsinArabidopsis thaliana

“…SAGs have been regulated by various environmental signals which include both abiotic and biotic stresses indicating various cross-talks between SAGs and stress responses (Lim et al ., 2007). Genes such as SAG12, SAG29 , and ORE1 play an important role in submergence mediated recovery by influencing senescence and chlorophyll breakdown in Arabidopsis (Huynh et al ., 2005, Seo et al ., 2011a, Yeung et al ., 2018, Bengoa Luoni et al ., 2019, Ueda et al ., 2020). To understand the molecular mechanism underlying leaf senescence in miR775 transgenic and galt9 lines, we compared the expression level of SAG12, SAG29 , and ORE1 during submergence stress.…”

Comparative Transcriptome-Based Mining of Senescence-Related MADS, NAC, and WRKY Transcription Factors in the Rapid-Senescence Line DLS-91 of Brassica rapa

“…Leaf yellowing, a distinct initial symptom of leaf senescence, is caused by chlorophyll depletion [ 51 ]. This reduction of chlorophyll is a characteristic reaction in the breakdown of photoreceptors during light depletion [ 1 , 86 ]. In the present study, we compared the chlorophyll content and photochemical efficiency (Fv/Fm) of leaf samples of DLS-42 and DLS-91 at three different phases of dark treatment ( Figure 2 A,B).…”

“…In the present study, we compared the chlorophyll content and photochemical efficiency (Fv/Fm) of leaf samples of DLS-42 and DLS-91 at three different phases of dark treatment ( Figure 2 A,B). The rapid loss of chlorophyll and reduction in photochemical efficiency observed in DLS-91 may have been due to the breakdown of photosynthetic components leading to diminished photosynthesis during dark treatment [ 1 , 86 ]. Similarly, leaves of Arabidopsis and barley subjected to dark treatment have been reported to exhibit a decline in chlorophyll and the Fv/Fm ratio according to the progression of dark exposure [ 11 , 85 ].…”

Effects of Exogenous Regulation of Ethylene and Abscisic Acid on Grain-Filling and Endosperm PCD of Wheat Under Drought Stress After Anthesis

“…The main differences between the three different treatments are concentrated at 15-35DPA. The effects of CN treatment on grain weight were mainly concentrated in the spraying period (15 DPA) and the middle-late lling period (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35). The grain weight in these two periods was signi cantly higher than that of CK.…”

“…The PCD of cereal crop's endosperm is greatly in uenced by endogenous hormones 28 . Previous studies have shown there is the interaction among the hormones, which constitute a very ne and complex regulatory network together with the external environment and their own developmental programs [29][30][31] . Furthermore, the main endogenous hormones ethylene and abscisic acid had signi cant effect on the endosperm PCD and grain lling process of cereal crops.…”