Morphological, Physiological and Molecular Characterization of Root Senescence in Barley

Résumé du livre

Plant root senescence is still an uncharacterized biological process. In this study, hydroponically cultivated barley plants were harvested weekly over a period of 53 days for structural, physiological and molecular analyses. We identified day 39 as an important transition point, as several events fell together: i) seminal roots stopped elongating and root epidermal and cortical tissues started decaying, ii) nitrate uptake capacity started decreasing, iii) remobilization of phosphorus and zinc was initiated. This coincided exactly with a sudden increase in abscisic acid (ABA) levels in seminal roots, which was confirmed by enhanced transcript levels of ABA biosynthesis genes. To identify possible regulators of root senescence, 60K barley microarrays were used for transcriptome analysis of the apical and basal root zone. Several NAC-, WRKY- and AP2-type transcription factors (TFs) were identified, which showed strong up-regulation just before root senescence set in. The present study indicates that root senescence is a highly coordinated developmental process, which involves an interplay of TFs and phytohormones.