Physiological and Proteomic Changes in the Apoplast Accompany Leaf Senescence in Arabidopsis

MOLINA AGOSTINI, MARÍA CELESTE; BORNIEGO, MARÍA LUCÍA; MARTÍNEZ, DANA; GUIAMET, JUAN JOSÉ; MOLINA AGOSTINI, MARÍA CELESTE; BORNIEGO, MARÍA LUCÍA; MARTÍNEZ, DANA; GUIAMET, JUAN JOSÉ

Frontiers in Plant Science

Frontiers Media SA

Lugar: Lausana; Año: 2020 vol. 10 p. 1 - 20

1664-462X

The apoplast, i.e. the cellular compartment external to the plasma membrane,undergoes important changes during senescence. Apoplastic fluid volumeincreases quite significantly in senescing leaves, thereby diluting its contents.Its pH elevates by about 0.8 units, similar to the apoplast alkalization inresponse to abiotic stresses. The levels of 159 proteins decrease, whereas 24proteins increase in relative abundance in the apoplast of senescing leaves.Around half of the apoplastic proteins of non-senescent leaves contain aN-terminal signal peptide for secretion, while all the identified senescence-associatedapoplastic proteins contain the signal peptide. Several of the apoplasticproteins that accumulate during senescence also accumulate in stress responses,suggesting that the apoplast may constitute a compartment where developmentaland stress-related programs overlap. Other senescence-related apoplasticproteins are involved in cell wall modifications, proteolysis, carbohydrate, ROSand amino acid metabolism, signaling, lipid transport, etc. The most abundant senescence-associatedapoplastic proteins, PR2 and PR5 (e.g. pathogenesis related proteins PR2 andPR5) are related to leaf aging rather than to the chloroplast degradation program,as their levels increase only in leaves undergoing developmental senescence, butnot in dark-induced senescent leaves. Changes in the apoplastic space may be relevantfor signaling and molecular trafficking underlying senescence.