Differential biosynthesis and cellular permeability explain longitudinal gibberellin gradients in growing roots

Abstract

Control over cell growth by mobile regulators underlies much of eukaryotic morphogenesis. In plant roots, cell division and elongation are separated into distinct longitudinal zones and both division and elongation are influenced by the growth regulatory hormone gibberellin (GA). Previously, a multicellular mathematical model predicted a GA maximum at the border of the meristematic and elongation zones. However, GA in roots was recently measured using a genetically encoded fluorescent biosensor, nlsGPS1, and found to be low in the meristematic zone grading to a maximum at the end of the elongation zone. Furthermore, the accumulation rate of exogenous GA was also found to be higher in the elongation zone. It was still unknown which biochemical activities were responsible for these mobile small molecule gradients and whether the spatiotemporal correlation between GA levels and cell length is important for root cell division and elongation patterns. Using a mathematical modeling approach in combination with high-resolution GA measurements in vivo, we now show how differentials in several biosynthetic enzyme steps contribute to the endogenous GA gradient and how differential cellular permeability contributes to an accumulation gradient of exogenous GA. We also analyzed the effects of altered GA distribution in roots and did not find significant phenotypes resulting from increased GA levels or signaling. We did find a substantial temporal delay between complementation of GA distribution and cell division and elongation phenotypes in a GA deficient mutant. Together, our results provide models of how GA gradients are directed and in turn direct root growth.

Strigo-D2 – a bio-sensor for monitoring the spatio-temporal pattern of strigolactone signaling in intact plants

“…Considering its specificity and sensitivity toward SL signaling, the Strigo-D2 sensor may be useful for addressing this question. Another example for sensor utility may be the establishment of computational models for SL signaling patterns based on dynamic sensor outputs as done previously for gibberellin [65]. Overall, we assume that the dynamic nature of Strigo-D2 will facilitate quantitative determination of SL signaling for developing a deeper understanding of SL biology.…”

The Contrivance of Plant Growth Promoting Microbes to Mitigate Climate Change Impact in Agriculture

“…Regulation of cell membrane permeability and thus control of water movement through organs is an important adaptive mechanism under osmotic stress, caused by high salinity [10,72]. The accumulation of proteins or amino acids in leaves helps protect cell structures from denaturation in the event of dehydration.…”

“…However, stomata that are closed for too long reduce photosynthetic activity and accelerate aging [ 78 ]. GA plays an important role in regulating important processes in the overall plant development, including seed germination, stem elongation and flowering [ 10 ]. Auxins can initiate root growth, postpone leaf senescence and promote stem elongation under normal conditions [ 6 ], while cytokinin improves cell proliferation and enlargement and the division of chloroplasts, and simultaneously reduces stomatal closure and delay leaf senescence.…”

“…The beneficial effects on the plant through interaction with PGPB can be achieved both directly as well as indirectly [ 10 , 79 ]. Direct mechanisms are based on the production of plant growth promoting substances or biofertilization by mobilizing mineral soil components [ 115 ].…”

“…This special mixture secreted by plant roots contains low-molecular weight organic substances, such as carbohydrates, amino acids, fatty acids, organic acids, vitamins and a small amount of secondary metabolites [ 8 , 9 ]. The extremely carbon-rich root exudates create a unique space with maximum bacterial activity compared to the bulk soil [ 7 , 10 ]. The nature of secreting exudates and various genetic regulations can influence the structure of bacterial community in the soil [ 2 ].…”