The Intensity of Manganese Deficiency Strongly Affects Root Endodermal Suberization and Ion Homeostasis

Abstract

Manganese (Mn) deficiency affects various processes in plant shoots. However, the functions of Mn in roots and the processes involved in root adaptation to Mn deficiency are largely unresolved. Here, we show that the suberization of endodermal cells in barley (Hordeum vulgare) roots is altered in response to Mn deficiency, and that the intensity of Mn deficiency ultimately determines whether suberization increases or decreases. Mild Mn deficiency increased the length of the unsuberized zone close to the root tip, and increased the distance from the root tip at which the fully suberized zone developed. By contrast, strong Mn deficiency increased suberization closer to the root tip. Upon Mn resupply, suberization was identical to that seen on Mn-replete plants. Bioimaging and xylem sap analyses suggest that the reduced suberization in mildly Mn-deficient plants promotes radial Mn transport across the endodermis at a greater distance from the root tip. Less suberin also favors the inwards radial transport of calcium and sodium, but negatively affects the potassium concentration in the stele. During strong Mn deficiency, Mn uptake was directed toward the root tip. Enhanced suberization provides a mechanism to prevent absorbed Mn from leaking out of the stele. With more suberin, the inward radial transport of calcium and sodium decreases, whereas that of potassium increases. We conclude that changes in suberization in response to the intensity of Mn deficiency have a strong effect on root ion homeostasis and ion translocation.

The molecular–physiological functions of mineral macronutrients and their consequences for deficiency symptoms in plants

“…The root endodermis tends to become more suberised under K deficiency (Fig. 7.1), a process triggered by ABA (Barberon et al ., 2016) and affecting the translocation of K + (Chen et al ., 2019).…”

Suberin plasticity to developmental and exogenous cues is regulated by a set of MYB transcription factors

“…While these lines showed a dramatic suberin reduction and were extremely important to distinguish between Casparian strip and suberin defects, we cannot exclude that artificially expressing the cutinase CDEF1 in the endodermis would not lead to additional defects. Moreover, being highly plastic in response to nutrient availability (6, 14, 21-25), suberin defects described in non-stressed conditions can in some case be exacerbated or absent in stressed conditions (25). To fully understand suberin function in the endodermis we crucially need better and more specific mutants and lines with constitutively enhanced and reduced endodermal suberization.…”

“…Suberin plasticity in response to abiotic stresses such as drought, salt, waterlogging or cadmium, while observed in roots in many species, (20, 46, 47, 53), only recently started to be characterized at the molecular level. This topic gained increasing interest in the past few years after observing that endodermal suberin is even more plastic than previously thought, and not only overproduced in toxic environments but also tightly modulated in response to mineral deficiencies (6, 14, 21-25), to Casparian strip defects (9, 10, 12, 14, 16, 17) and during biotic interactions (25-28). In light of the plethora of signals controlling suberization, understanding the interaction between these pathways is critical.…”

Unraveling the mechanisms controlling Cd accumulation and Cd‐tolerance in Brachiaria decumbens and Panicum maximum under summer and winter weather conditions

“…This is in agreement with Kopittke et al (2010) who observed lower Mn uptake by the roots of B. decumbens exposed to Cd, and Rabêlo and Borgo (2016) that observed lower cationic micronutrients uptake by grasses exposed to Cd. The intensity of Mn deficiency strongly affects the root endodermis suberization and ion homeostasis which is important for plants to cope with Cd‐induced stress (Chen et al 2019, Carvalho et al 2020). Besides Mn and Zn, the concentrations of P, K, Ca and S in the roots of B. decumbens grown in the summer condition were lower on the Cd‐polluted soil (Table 1).…”