Regulation of senescence-associated protease genes by sulphur availability according to barley (Hordeum vulgare L.) phenological stage

CINTIA G. VELIZ; MARIA VICTORIA CRIADO; FLORENCIA GALOTTA; IRMA N. ROBERTS; CAPUTO SUAREZ, CARLA PAULA

ANNALS OF BOTANY

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2020

0305-7364

? Background and Aims Proteases are responsible for protein degradation during leaf senescence, allowing nutrientsto be redirected to sink tissues. In a previous work, we reported that sulphur deficiency produced a delay inthe leaf senescence of barley (Hordeum vulgare L.) plants, at both vegetative and reproductive stages. In this work,we analyse the effect of sulphur deficiency on the expression of several genes coding for proteases of differentcatalytic groups, which have been strongly associated with leaf senescence.? Methods Four independent experiments were performed in order to impose low sulphur availability conditions:one of steady-state sulphur deficiency during the vegetative stage and three of sulphur starvation during vegetativeand reproductive stages.? Key Results Sulphur deficiency inhibited or reduced the senescence-associated induction of seven of theeight proteases analysed. Their induction, as well as senescence and phloem amino acid remobilization, could beachieved with senescence inducers such as methyl-jasmonate (a hormonal stimulus) and darkness, but with differentrates of induction dependent on each gene. Sulphur deficiency also exerted an opposite effect on the expressionof two cysteine-protease genes (HvSAG12 and HvLEGU) as well as on one serine-protease gene (HvSUBT)according to leaf age and plant phenological stages. All three genes were induced in green leaves but were repressedin senescent leaves of sulphur-deficient plants at the vegetative stage. At the reproductive stage, bothcysteine-proteases were only repressed in senescent leaves, while the serine-protease was induced in green andsenescent leaves by sulphur deficiency.? Conclusions Our results highlight the relevance of adequate sulphur nutrition in order to ensure leaf senescenceonset and induction of protease genes, which will consequently impact on grain protein composition and quality.In addition, our results provide evidence that leaf age, plant developmental stage and the nature of the stress modulatethe sulphur responses.