Crosstalk Between Abiotic and Biotic Stresses Responses and the Role of Chloroplast Retrograde Signaling in the Cross-Tolerance Phenomena in Plants

In natural environment plants are simultaneously exposed to multivariable abiotic and biotic stresses. Typical abiotic stresses are changes in temperature, light intensity and quality, water stress (drought, flood), microelements availability, salinity, air pollutants and others. Biotic stresses are caused by other organisms such as pathogenic bacteria and viruses, or by parasitic insects and plants. This review presents the state of the art of the programmed cell death in the cross-tolerance phenomena and its conditional molecular and physiological regulators, which are involved in simultaneous regulation of plant acclimation, defense and developmental responses. It highlights the role of the absorbed energy in excess and its dissipation as heat in induction of the chloroplast-retrograde electrical, phytohormonal, reactive oxygen species signaling and heat shock related pathways in connection to activation of the molecular regulators of plant growth, yield and cell wall development. It also discusses how systemic and network-acquired acclimation and acquired systemic resistance are mutually regulated and demonstrates the role of non-photochemical quenching and the dissipation of absorbed energy in excess as heat in the cross-tolerance phenomenon. Finally new evidences that in plants evolved one molecular system to regulate cell death, acclimatization and cross-tolerance to abiotic and biotic stress are presented and discussed.