Exodermis and Endodermis Respond to Nutrient Deficiency in Nutrient-Specific and Localized Manner

Abstract

The exodermis is a common apoplastic barrier of the outer root cortex, with high environmentally-driven plasticity and a protective function. This study focused on the trade-off between the protective advantages provided by the exodermis and its disadvantageous reduction of cortical membrane surface area accessible by apoplastic route, thus limiting nutrient acquisition from the rhizosphere. We analysed the effect of nutrient deficiency (N, P, K, Mg, Ca, K, Fe) on exodermal and endodermal differentiation in maize. To differentiate systemic and localized effects, nutrient deficiencies were applied in three different approaches: to the root system as a whole, locally to discrete parts, or on one side of a single root. Our study showed that the establishment of the exodermis was enhanced in low–N and low–P plants, but delayed in low-K plants. The split-root cultivation proved that the effect is non-systemic, but locally coordinated for individual roots. Within a single root, localized deficiencies didn’t result in an evenly differentiated exodermis, in contrast to other stress factors. The maturation of the endodermis responded in a similar way. In conclusion, N, P, and K deficiencies strongly modulated exodermal differentiation. The response was nutrient specific and integrated local signals of current nutrient availability from the rhizosphere.

Innovation, conservation, and repurposing of gene function in root cell type development

“…Our observation of exodermal nitrogen gene regulation is the first report of this molecular function for this cell type. However, nitrogen inducibility of exodermis differentiation has been observed in other species, suggesting that ll nitrogen signaling also plays a role in exodermal differentiation (Armand et al, 2019;Namyslov et al, 2020;Schreiber et al, 2005). Our data also support repurposing of SlKNAT1 function to the primary root xylem.…”

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

“…Suberin, however, is not only regulated by endogenous developmental factors surveilling Casparian strip integrity. Pointing toward a very central role of suberin in plants’ adaptation to their environment, endodermal suberization is also highly regulated by nutrient availability and the hormones ethylene and abscisic acid (ABA) ( 6 , 14 , 20 – 25 ), as well as during biotic interactions ( 25 – 28 ). How suberin is regulated in response to developmental and exogenous clues remains poorly understood.…”

Convergent evolution of gene regulatory networks underlying plant adaptations to dry environments

“…The roots of several species also develop an exodermis below the epidermis, which is a specialized type of hypodermis with Casparian bands and suberin lamellae depositions (Enstone et al, 2002 ; Perumalla et al, 1990 ). The exodermis functions as a dynamic barrier not only against water loss under drought and salinity but also against loss of oxygen under anoxic conditions, against penetration of ions and heavy metals and against pathogen infections (Aloni et al, 1998 ; Damus et al, 1997 ; Ejiri & Shiono, 2019 ; Enstone et al, 2002 ; Líška et al, 2016 ; Namyslov et al, 2020 ; Ranathunge et al, 2011 ; Tylová et al, 2017 ). At the same time, the development of exodermis barriers has its downside as it may impair the uptake of nutrients and interaction with beneficial microbes (Kamula et al, 1994 ).…”