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Quality Footprinting Of Horticultural Crops Using NADPH

Bio-sensors can monitor and communicate information about live biological processes. Both SoNAR and iNAP Sensors can be used to examine NADPH dynamics in-vivo because of their enhanced sensitivity and brightness.

The Basics

NADPH is an energy-carrying molecule. Its produced from NADP(nicotinamide adenine dinucleotide phosphate), which is a coenzyme that acts as an electron carrier, accepting electrons and hydrogen atoms to form NADPH.

In the case of plants, NADPH is produced during the first stage of photosynthesis. It basically acts as an energy-carrying molecule in plants. 

 

Importance of NADPH

  • NADPH could be used as quality foot-printing in horticulture crops marketability

  • NADPH supply is beneficial for retaining the sensory and nutritional quality, 
  • Conferring Post-harvest stresses tolerance is possible by NADPH supply.
  • It is crucial for governing Fruit ripening.

Post-harvest physiologists define 3 stages in the life span of fruits and vegetables- Maturation, Ripening, Senescence.

 

Maturation

Maturation is indicative of the fruit being ready for harvest. Ripening follows or sometimes overlaps maturation. This renders the produce edible. Senescence is the last stage, characterized by natural degradation of fruit or vegetable.

What actually happens during ripening?

  1. Increase in the breakdown of starch
  2. Increase in the number of simple sugars (glucose, sucrose)
  3. Cell walls begin to break down
  4. Loss of fluid in fruits, leading to a decrease in turgor pressure
  5. Shrivelling of fruits

To maintain post-harvest quality, low-temperature storage is widely used to delay senescence in fruit ripening. However, this can result in damage such as fruit wounding and fungal decay.  The intra-cellular reducing power of reduced Nicotinamide adenine Di-nucleotide phosphate (NADPH), a key indicator of cellular redox status, is essential in many metabolic pathways.

The supply of intracellular NADPH at the post-harvest stage could enhance the marketability of horticulture crops. NADPH processes provide metabolic signatures to attenuate stress conditions, delay senescence, and preserve the sensory and nutritional quality of post-harvest crops.

It also plays a crucial role in fungal decay tolerance. As the post-harvest fruits are also affected by fungal diseases which cause significant economic losses. The various strategies used including the exogenous application of chemical fungicides involve the use of NADPH in many cases.

NADPH is a co-factor, used to donate electrons and hydrogens to reactions catalyzed by some enzymes. The enzymes involved in Anabolic pathways create large molecules using NADPH while enzymes involved in the breakdown of molecules use the analogue NADH. Mitochondria use NADH during Oxidative Phosphorylation, while many Cytosol enzymes synthesize large molecules using NADPH.

During their post-harvest life, horticulture crops are affected by a vast range of processes, ranging from plant senescence and fungal infection. Cold storage periods might also result in chilling injuries. Since NADPH is a strong reducing agent, its supply needs to be optimized in order to maintain multiple metabolic pathways involved in natural ripening and post-harvest life of horticulture crops.

For the generation and functioning of the cellular NADPH pool, a series of reactions are involved. The homeostasis of NADPH integrates and coordinates different metabolic pathways involved in the physiological processes.

For several years, monitoring these pyrimidine Di-nucleotides in-vivo and in-situ was challenging but recent advancements and development of genetically encoded fluorescent Bio-sensors have paved the way for real-time imaging of NAD+/NADPH and NADP+/NADPH.

 

Technology Used

A Bio-sensor is an analytical device that combines a biological component to a detector. It can monitor and communicate information about live biological processes. Some examples of Bio-sensors designed for in-situ monitoring of Pyrimidine Di-nucleotides are

SoNAR Sensor: It is one of the most responsive and sensitive NAD+/NADH sensors available

iNAP Sensor: iNAP is highly selective towards NADPH and fluorescence

Both these sensors can be used to examine NADPH dynamics in-vivo because of their enhanced sensitivity and brightness. Some other examples of Bio-sensors are Peredox sensor, Yap 1 p, Luc sensor, cpVenus sensor, etc. These Bio-sensors are used to examine environmental contamination and pollution detection. However, the use of these Bio-sensors for horticulture is being examined.

The conventional methods of monitoring these Redox metabolism states are a challenge as the processes require sophisticated equipment. The development of genetically encoded fluorescent sensors has pioneered the next generation of real-time monitoring in vivo and in situ of the pyrimidine Di-nucleotides in cells. The Bio-sensors are easily replicable and serve a faster and convenient means of obtaining data.

It plays a crucial role in cellular Redox reaction and is also involved in processes like Photosynthesis, Carbohydrate Activity, Reactive Oxygen Species (ROS), and Fatty Acid Metabolisms, Pentose Phosphate Pathway, Jasmonic acid biosynthesis, as well as the Shikimate and phenylpropanoid pathways operating in secondary metabolite biosynthesis

Thus, Intracellular NADPH metabolism could provide a physiological, biochemical, and molecular footprint for the sensory and nutritional quality of post-harvest horticulture crops.

 

Reference

K. Kyere-Yeboah, J. Denteh, K. Liu, P. Ye, E.-B. Gao, Monitoring
Nicotinamide Adenine Dinucleotide and its phosphorylated redox metabolism using genetically encoded
fluorescent biosensors, Sensing and Bio-Sensing Research (2019)

as: Aghdam, M.S., Palma, José.M., Corpas, F.J., NADPH as a quality footprinting
in horticultural crops marketability, Trends in Food Science & Technology (2020),

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