The dependence of leaf senescence on the balance between 1‐aminocyclopropane‐1‐carboxylate acid synthase 1 (ACS1)‐catalysed ACC generation and nitric oxide‐associated 1 (NOS1)‐dependent NO accumulation in Arabidopsis

Abstract

Ethylene and nitric oxide (NO) act as endogenous regulators during leaf senescence.Levels of ethylene or its precursor 1-aminocyclopropane-1-carboxylate acid (ACC) depend on the activity of ACC synthases (ACS), and NO production is controlled by NO-associated 1 (NOA1). However, the integration mechanisms of ACS and NOA1 activity still need to be explored during leaf senescence.• Here, using experimental techniques, such as physiological and molecular detection, liquid chromatography-tandem mass spectrometry and fluorescence measurement, we investigated the relevant mechanisms.• Our observations showed that the loss-of-function acs1-1 mutant ameliorated age-or dark-induced leaf senescence syndrome, such as yellowing and loss of chlorophyll, that acs1-1 reduced ACC accumulation mainly in mature leaves and that acs1-1-promoted NOA1 expression and NO accumulation mainly in juvenile leaves, when compared with the wild type (WT). But the leaf senescence promoted by the NO-deficient noa1 mutant was not involved in ACS1 expression. There was a similar sharp reduction of ACS1 and NOA1 expression with the increase in WT leaf age, and this inflection point appeared in mature leaves and coincided with the onset of leaf senescence.• These findings suggest that NOA1-dependent NO accumulation blocked the ACS1induced onset of leaf senescence, and that ACS1 activity corresponds to the onset of leaf senescence in Arabidopsis.

Nitric Oxide Alters the Pattern of Auxin Maxima and PIN-FORMED1 During Shoot Development

“…A visual analysis of NO homeostasis mutants showed apparent defects associated with leaf morphology ( Figures 2A – E ) and structural characteristics, like the number of serrations ( Figure 2F ). The reduced number of true leaves in noa1-1 mutant showed a pale phenotype, with premature senescence in the oldest ones, as previously reported ( Liu and Guo, 2013 ; Lv et al, 2019 ), and a low number of serrations. On the opposite, the NO overaccumulator cue1/nox1 exhibited a high number of smaller leaves, with a remarkable venosa phenotype, characterized by a different pigmentation between the green veins and the pale interveinal regions (also known as reticulate ; Berná et al, 1999 ; Robles and Micol, 2001 ), and a greater number of serrations ( Figure 2F ).…”

Gasotransmitters in Action: Nitric Oxide-Ethylene Crosstalk during Plant Growth and Abiotic Stress Responses

“…Moreover, leaf senescence is accelerated whenever endogenous NO content is reduced, such as in NO-deficient mutants [107] and transgenic plants overexpressing a NO-degrading dioxygenase (NOD) gene [108]. Young plant tissues usually display higher NO levels, which progressively decrease as plant organs mature [109,110], with ET displaying an opposite trend [111]. Therefore, plant ET and NO metabolisms seem to be inversely influenced by tissue aging.…”

From Chloroplast Biogenesis to Chlorophyll Accumulation: The Interplay of Light and Hormones on Gene Expression in Camellia sinensis cv. Shuchazao Leaves

“…It has been suggested that the two hormones (CTK and GA) serve to regulate HY5 at the protein level and that HY5 promotes photomorphogenesis partly by modulating auxin, GA and abscisic acid signaling (Lau and Deng, 2010). Ethylene (ETH) and its precursor (1aminocyclopropane-1-carboxylate acid, ACC) play critical roles in leaf senescence, root elongation and protecting cotyledons from photooxidative damage when the seedlings are exposed to light Han et al, 2019;Lv et al, 2019). Ethylene Insensitive 3/EIN3-Like 1 (EIN3/EIL1) is the master transcription factor in the ethylene signaling pathway (Guo and Ecker, 2004), which markedly inhibits the accumulation of pchlide and directly binds to the promoters of PORA and PORB to activate their gene expression (Zhong et al, 2014).…”