Root proteases: reinforced links between nitrogen uptake and mobilization and drought tolerance

Abstract

Integral subcellular and cellular functions ranging from gene expression, protein targeting and nutrient supply to cell differentiation and cell death require proteases. Plants have unique organelles such as chloroplasts composed of unique proteins that carry out the unique process of photosynthesis. Hence, along with proteases common across kingdoms, plants contain unique proteases. Improved knowledge on proteases can lead to a better understanding of plant development, differentiation and death. Because of their importance in multiple processes, plant proteases are actively studied. However, root proteases specifically are not as well studied. The associated rhizosphere, organic matter and/or inorganic matter make roots a difficult system. Yet recent research conclusively demonstrated the occurrence of endocytosis of proteins, peptides and even microbes by root cells, which, hitherto known for specialized pathogenesis or symbiosis, was unsuspected for nutrient uptake. These results reinforced the importance of root proteases in endocytosis or root exudate-mediated nutrient uptake. Rhizoplane, rhizosphere or in planta protease action on proteins, peptides and microbes generates sources of nitrogen, especially during abiotic stresses such as drought. This article highlights the recent research on root proteases for nitrogen uptake and the connection of the two to drought-tolerance mechanisms. Drought-induced proteases in rice roots, as known from rice expression databases, are discussed for future research on certain M50, Deg, FtsH, AMSH and deubiquitination proteases. The recent emphasis on linking drought and plant hydraulics to nutrient metabolism is illustrated and connected to the value of a systematic study of root proteases in crop improvement.

Soil moisture variations affect short‐term plant‐microbial competition for ammonium, glycine, and glutamate

“…Drought causes a decline in the activity of some enzymes, for example nitrate reductases (Cornic and Massacci ), and induces others, such as root proteases, facilitating amino acid uptake (Kohli et al. ). That may provide an additional explanation to the higher amino acid uptake in the dried–rewetted soil.…”

“…Amino acid N is potentially a more cost-effective N source under conditions when the leaf net CO 2 uptake decreases because of stomatal closure, for example during drought (Cornic and Massacci 1996;Schmidt and Stewart 1999). Drought causes a decline in the activity of some enzymes, for example nitrate reductases (Cornic and Massacci 1996), and induces others, such as root proteases, facilitating amino acid uptake (Kohli et al 2012). That may provide an additional explanation to the higher amino acid uptake in the dried-rewetted soil.…”

Is N-feedback involved in the inhibition of nitrogen fixation in drought-stressedMedicago truncatula?

“…Furthermore, given the various structural and functional classes of proteases and their specific regulatory mechanisms, it is difficult to generalize their role in a process, with certain drought-tolerant plants exhibiting up-regulation of some proteases and down-regulation of others (Kohli et al ., 2012). In the present case, the fact that there is not a clear shift in total protease activity is in agreement with the relatively stable measurements of total soluble protein (Fig.…”

The Role of Plants in the Effects of Global Change on Nutrient Availability and Stoichiometry in the Plant-Soil System

“…The enhancement of mycorrhizal symbiosis improves the capacity of plants to take up both water and nutrients (Ruiz-Lozano et al, 1995;Alvarez et al, 2009;Wu et al, 2011a). Drought can also increase the allocation of resources to roots (Huang, 2001;Wittenmayer and Merbach, 2005;Suralta, 2010), the acceleration of turnover of fine roots (Meier and Leuschner, 2008), and an increased production of root exudates, contributing to increased chelation and uptake of nutrients (Henry et al, 2007;Kohli et al, 2012). Mycorrhization is positively correlated with an enhanced antioxidant metabolism in plants ( Ruiz-Lozano et al, 1996).…”