Proteins as nitrogen source for plants: a short story about exudation of proteases by plant roots

Abstract

Interest in the problem of plant nitrogen nutrition is increasing. Certain plants can use not only inorganic nitrogen, but also intact amino acids and short peptides. According to our studies, the roots of several agricultural and wild-living plants are able to exude proteases and by using them to create a pool of accessible N. This mini-review offers an overview of the problem of protease exudation by plant roots and its potential role in plant nitrogen nutrition.

Keywords: amino acids; nutrient uptake; organic nitrogen; plant nitrogen nutrition; protease exudation.

Figure 1

Proteolytic activity of the root-secreted proteases of seedlings of different plant species grown in sterile conditions (means ± standard error of the mean, n = 10); azocasein was used as a substrate for proteases. Modified from reference .

Figure 2

Chromatograms of the degradation products of casein by root-secreted proteases, (A) casein with denatured root-secreted proteases (no digestion), (B) casein incubated for 1 hour with root-secreted proteases. Molecular masses are marked above the peaks. Modified from reference .

Figure 3

Fresh weight of shoot (grey columns) and proteolytic activity (black columns) in the culture medium of seedlings cultivated on different media (means ± standard error of the mean, n = 6). Azocasein was used as a substrate for proteases. Statistically significant differences (p < 0.05) between fresh weight are indicated by different letters, and significant differences between proteolytic activity are indicated by capitals. MS—Murashige and Skoog medium, MS-IN—Murashige and Skoog medium without inorganic nitrogen, FW—fresh weight. Modified from reference .