The Role of Strigolactones and Their Potential Cross-talk under Hostile Ecological Conditions in Plants

Abstract

The changing environment always questions the survival mechanism of life on earth. The plant being special in the sense of their sessile habit need to face many of these environmental fluctuations as they have a lesser escape option. To counter these adverse conditions, plants have developed efficient sensing, signaling, and response mechanism. Among them the role of phytohormones in the management of hostile ecological situations is remarkable. The strigolactone, a newly emerged plant hormone has been identified with many functions such as growth stimulant of parasitic plants, plant architecture determinant, arbuscular mycorrhiza symbiosis promoter, and also in many other developmental and environmental cues. Despite of their immense developmental potential, the strigolactone research in the last few years has also established their significance in adverse environmental condition. In the current review, its significance under drought, salinity, nutrient starvation, temperature, and pathogenic assail has been discussed. This review also opens the research prospects of strigolactone to better manage the crop loss under hostile ecological conditions.

Keywords: biotic stress; drought; nutrient starvation; salinity; strigolactone; temperature.

Figure 1

Strigolactone (SL) Biosynthetic pathway: figure shows the biosynthetic pathway of SL production and key enzymes involved in biosynthesis. SL biosynthesis occurs in two separate compartments, plastid and cytosol. Biosynthesis starts in plastid with the conversion of trans-β-carotene to (Z)-(R)-carlactone (CL) involving three intermediate steps catalyzed by trans/9-cys-β-carotene Isomerase, CCD7, and CCD8, respectively. Carlactone further moves to cytosol and there with the help of Cytochrome P450 monooxygenase (MAX1) and several other unidentified enzymes it is further converted to different other SLs. Enzymes involved in this biosynthetic pathway in different plants are named accordingly like Arabidopsis (MAX), Rice (D), and in Pea (RMS).

Figure 2

Strigolactone triggered response under hostile ecological conditions: picture shows the stress triggered biosynthesis and signaling of SLs. SLs under abiotic and biotic stress conditions provide resistance to plants. Under water stress SLs inhibit shoot growth (a cross talk with cytokinin) while enhance lateral root growth to increase the uptake of water. In a cross talk with ABA, SLs regulate stomatal density and release seed dormancy. SLs enhance arbuscular mycorrhizal (AM) association to increase mineral uptake under Nitrogen and Phosphorus deficiency. Under biotic stress condition SLs provide tolerance against pathogen infection.