Fig. 3

Hormonal and environmental regulation of leaf senescence. YCCA6 is responsible for the biosynthesis of auxin which inhibits leaf senescence in young leaves. The auxin responsive genes SAUR36, ARF2, and ANT2 inhibit leaf senescence in young leaves. OsCKX11 degrades cytokinins in rice during leaf senescence. Arabidopsis MYB2 regulates plant senescence by affecting the cytokinin homeostasis. Activation of the cytokinin receptor AHK3 (ORE12) significantly delays leaf senescence. DELLA proteins interact with TFs WRKY45 and WRKY6 and suppress leaf senescence. ABA receptor PYL9 functions in response to ABA and actives signaling components including ABF2/3/4, ABI5/EEL and AtNAP to promote leaf senescence. SAG113 and AAO3 are two direct target genes of the AtNAP TF. Ethylene regulates leaf senescence through the EIN2-EIN3-miR164-ORE1 pathway. In addition, ORE1 promotes ethylene synthesis via activating ethylene biosynthesis gene ACS. JA induces leaf senescence via a signaling pathway involving COI1, JAZ proteins, MYC2/3/4 and NAC proteins ANAC019/055/072. SL induces leaf senescence through TFs ORE9/MAX2. WRKY family TFs WRKY28, 46, 55, 75 and the WHIRLY1 protein induce the expression of ICS1 for SA biosynthesis and SA induces S3H and S5H which convert SA to hydroxylated SA. SA induces ROS accumulation via the signaling pathway NPR1-PAD4-EDS1, promoting leaf senescence. Arabidopsis circadian evening complex (EC) negatively regulates JA-induced leaf senescence by suppress the expression of MYC2. PRR9 functions as a positive regulator of leaf senescence by repressing the transcription of miR164 and activating ORE1 expression. CCA1 counteracts leaf senescence by directly activating GLK2 and suppressing ORE1 expression. ELF3 and PhyB delay leaf senescence by suppressing the transcription and protein accumulation of PIF4/PIF5. Moreover, PIF4/PIF5 directly activates expression of EIN3, ABI5 and EEL. TF SOC1 is responsive to light and negatively regulates leaf senescence. Drought induces leaf senescence via activating the ABA signaling pathway. Pathogens induce the expression of WRKY TFs such as WRKY55, promote SA biosynthesis and ROS accumulation, leading to leaf senescence