In response to partial plant shading, the lack of phytochrome A does not directly induce leaf senescence but alters the fine-tuning of chlorophyll biosynthesis

Abstract

SummaryIn partially shaded plants, phytochrome A contributes to the adjustment of photosynthesis in shaded leaves but is not directly involved in the induction of leaf senescence

Fruits from ripening impaired, chlorophyll degraded and jasmonate insensitive tomato mutants have altered tocopherol content and composition

“…It can, therefore, be inferred from these results that the Chl biosynthesis machinery is still functional in R stage fruits. Changes in transcriptional regulation of Chl biosynthetic genes were previously reported in the Arabidopsis phytochrome A mutant (Brouwer et al, 2014). Induced leaf yellowing in this mutant correlates to the repression of Chl biosynthesis associated genes rather than to an increase of its catabolism.…”

A proteome map of a quadruple photoreceptor mutant sustains its severe photosynthetic deficient phenotype

“…The fact that the Chla/b ratios did not change in the quadruple mutant suggests that both types of photosystems were reduced to the same level. phyA and phyB single mutants have reduced total chlorophyll levels relative to the WT, but the Chla/b ratio did not change when the plants were grown under white light (Brouwer et al, 2014). Additionally, in shaded grown plants, total chlorophyll content was decreased, but the Chla/b ratios were unaffected (Murchie and Horton, 1997;Zivcak et al, 2014).…”

PHYTOCHROME-INTERACTING FACTOR 5 (PIF5) positively regulates dark-induced senescence and chlorophyll degradation in Arabidopsis

“…Red light is considered a negative signal for this process, because pulses of red light substantially delay dark-induced senescence [31]. Plants that overexpress the light receptors phytochrome A or B show delayed leaf yellowing [32,33], whereas the loss-of-function mutant phyB is hyposensitive to dark treatment [34], suggesting a role of phytochromes in the regulation of leaf senescence. Recently, two studies found that phytochromeinteracting transcription factors PIF4 and PIF5 are both positive factors of dark-induced senescence in Arabidopsis [3,35].…”