Water deficit induces chlorophyll degradation via the ‘PAO/phyllobilin’ pathway in leaves of homoio‐ (Craterostigma pumilum) and poikilochlorophyllous (Xerophyta viscosa) resurrection plants

Abstract

Angiosperm resurrection plants exhibit poikilo-or homoiochlorophylly as a response to water deficit. Both strategies are generally considered as effective mechanisms to reduce oxidative stress associated with photosynthetic activity under water deficiency. The mechanism of water deficit-induced chlorophyll (Chl) degradation in resurrection plants is unknown but has previously been suggested to occur as a result of non-enzymatic photooxidation. We investigated Chl degradation during dehydration in both poikilochlorophyllous (Xerophyta viscosa) and homoiochlorophyllous (Craterostigma pumilum) species. We demonstrate an increase in the abundance of PHEOPHORBIDE a OXYGENASE (PAO), a key enzyme of Chl breakdown, together with an accumulation of phyllobilins, that is, products of PAO-dependent Chl breakdown, in both species. Phyllobilins and PAO levels diminished again in leaves from rehydrated plants. We conclude that water deficit-induced poikilochlorophylly occurs via the well-characterized PAO/phyllobilin pathway of Chl breakdown and that this mechanism also appears conserved in a resurrection species displaying homoiochlorophylly. The roles of the PAO/phyllobilin pathway during different plant developmental processes that involve Chl breakdown, such as leaf senescence and desiccation, fruit ripening and seed maturation, are discussed. (2014). Water deficit induces chlorophyll degradation via the 'PAO/phyllobilin' pathway in leaves of homoio-(Craterostigma pumilum) and poikilochlorophyllous (Xerophyta viscosa) resurrection plants. Plant, Cell Environment, 37(11):2521-2531.

Relating Water Use to Tree Vitality of Populus euphratica Oliv. in the Lower Tarim River, NW China

“…Sap flow of vital poplar started to decrease from 19:00 p.m., which was 2 h later than the senesced poplar, which may have been decided by the physiological and morphological status of the tree itself. Hörtensteiner's study showed that chlorophyll content in tree leaves decreased when the tree leaves were senesced [50]; furthermore, Christ et al found that water shortage also induced decreasing chlorophyll in tree leaves [51], however, the lower chlorophyll content in tree leaves weakened the photosynthetic activity …”

Orthodox Seeds and Resurrection Plants: Two of a Kind?

“…In both X. humilis and X. viscosa, Chl degradation begins once leaf water content decreases below 80% RWC and continues to depletion in the air-dry state. During rehydration, Chl biosynthesis is induced rapidly, and the regeneration of thylakoids is apparent within 3 d (Ingle et al, 2008;Christ et al, 2014). This poikilochlorophyllous mechanism bears a strong resemblance to the degradation of Chl in maturing seeds.…”

“…1), such as Xerophyta humilis and X. viscosa, gradually dismantle their photosynthetic machinery, leading to almost Chlfree dehydrated leaves ( Fig. 2; Porembski, 2011;Tuba and Lichtenthaler, 2011;Beckett et al, 2012;Christ et al, 2014). In both X. humilis and X. viscosa, Chl degradation begins once leaf water content decreases below 80% RWC and continues to depletion in the air-dry state.…”

“…This poikilochlorophyllous mechanism bears a strong resemblance to the degradation of Chl in maturing seeds. In PDT, Chl, LHCb1 (a component of the lightharvesting antennae of PSII), and PsbA (a subunit of the core complex of PSII) are degraded during dehydration and resynthesized during rehydration, indicating the involvement of the pheophorbide a oxygenase (PAO)/ phyllobilin pathway (Christ et al, 2014). Chl degradation during seed maturation also follows the PAO/ phyllobilin pathway and is partly controlled by ABA through the regulation of NON-YELLOW COLORING1 (NYC1; encoding a Chl b reductase isoform involved in Chl catabolism) expression (Nakajima et al, 2012).…”

Ecophysiological responses to drought followed by re-watering of two native Chilean swamp forest plants: Myrceugenia exsucca (DC.) O. Berg and Luma chequen (Molina) A. Gray

“…This could be related with the lower specific leaf area of M. exsucca, respect to L. chequen which could involve a higher density of PS and a higher probability of photochemicals process in the same area (Vile et al 2005, He et al 2013. Drought reduction in pigment content has been considered a typical symptom of oxidative stress, as a result of either slow synthesis or fast breakdown (Christ et al 2014).…”