Switch from heterotrophy to autotrophy of apple cotyledons depends on NO signal

Abstract

Main conclusionNO accelerates transition of germinated embryos from heterotrophy to autotrophy by stimulation of chloroplasts maturation. NO-mediated autotrophy of apple seedlings correlates to increased content of RuBisCO small subunit and improvement of parameters of chlorophyllafluorescence.Nitric oxide (NO) acts as signaling molecule involved in regulation of various physiological processes in plants, although its involvement in cotyledons greening is poorly recognized. To identify the importance of NO signal for plant growth and development we investigated the effects of short-term application of NO at various developmental stages of seedlings of apple (Malus domestica Borkh.) on cotyledons’ chlorophyll a to b ratio, chlorophyll a fluorescence, photosynthetic activity, carbohydrates and RuBisCO both subunits content. NO-dependent biochemical alterations were linked to cytological observation of developing plastids in cotyledons of apple plants. Abnormal plantlets developing from dormant apple embryos are characterized by anatomical malformations of cotyledons. Short-term pre-treatment with NO of isolated embryos or seedlings with developmental anomalies resulted in formation of plants with cotyledons of equal size and chlorophyll content; these responses were blocked by NO scavenger. NO independently of time point of application accelerated embryos transition from heterotrophy to autotrophy by stimulation of photosynthetic activity, improvement of parameters of chlorophyll a fluorescence (Fv/Fm, Fv/F0) and increased content of RuBisCO small subunit. Further analysis showed that NO application modified glucose and hydrogen peroxide concentration in cotyledons. Beneficial effect of NO on development of seedlings without any abnormalities was manifested at ultrastructural level by decline in amount of proplastids and induction of formation and maturation of chloroplasts. Our data suggest that progress of autotrophy of young seedlings is governed by NO acting as stimulator of chloroplast-to-nucleus signaling.

Differential Molecular Responses of Rapeseed Cotyledons to Light and Dark Reveal Metabolic Adaptations toward Autotrophy Establishment

“…Lipid oxidation and photorespiration result in a burst of reactive oxidative species (ROS), e.g., H 2 O 2 . Although ROS signaling plays positive roles in plastid differentiation after seed germination in conjunction with ABA and NO regulation ( Kim et al, 2009 ; Krasuska et al, 2015 ), the accumulated ROS is harmful to the cellular structure and metabolism. Several systems are employed in the cell to eliminate oxidative damage, especially for redox related proteins.…”

Nitric Oxide as a Remedy against Oxidative Damages in Apple Seeds Undergoing Accelerated Ageing

“…The germination rate of NO-treated embryos was higher, and developing seedlings exhibited less morphological abnormalities than the control ( Figure 2 and Figure 3 ). Previously, we have demonstrated the equal greening of cotyledons of abnormal apple seedlings after NO supplementation [ 50 ], proving an important mechanism of switching from heterotrophy to autotrophy. Similarly, NO stabilized photosynthetic pigments in cotyledons of soybean ( Glycine max L.), suggesting its role in ageing delay [ 51 ].…”

Modification of the endogenous NO level influences apple embryos dormancy by alterations of nitrated and biotinylated protein patterns

“…Fig. S1) (Gniazdowska et al 2007(Gniazdowska et al , 2010bKrasuska et al 2015b). In contrast, cPTIO supplementation into growing medium resulted in maintenance of embryo dormancy (Suppl.…”