Extracellular self-DNA induces local inhibition of growth, regulates production of reactive oxygen species, and gene expression in rice roots

Abstract

The capacity of extracellular self-DNA (esDNA) to inhibit growth is getting more research attention as this could be explored for several purposes, including the development of specific bioherbicides. While the inhibitory effect has been studied in several dicotyledon species, little is known about the effects and subsequent signaling processes in monocots. Here, we measured the growth, counted the number of lateral and crown roots, determined greenness index, quantified the production of O2.- and H2O2, and determined the expressions of genes encoding antioxidant enzymes (SODs and CATs) in rice (Oryza sativa L.), a model plant of monocots. After 7 d of germination, rice roots were exposed to 0, 75, and 150 µg cm-3 of esDNA. Inhibitory effect was found to be negatively correlated to esDNA concentration, as indicated by the length of primary roots. Interestingly, this negative effect was only observed in the directly exposed organ (root) but not in the length of shoot or fresh mass of the whole seedling. The percentage of greenness index of leaves and number of crown and lateral roots were also similar across treatments. However, esDNA exposure to root increased production of O2.- and H2O2 in the root. At the molecular level, the response was characterized by the decreased expression of the antioxidant genes SOD3, CATB, and CATC. These findings suggest that esDNA inhibits rice growth locally in, e.g. in treated roots, and the responses involve increased production of ROS and suppression of antioxidants. This study could be the basis for determining the combination of concentration and period of exposure that might significantly inhibit total growth of monocot weeds with a minimum effect on the crop.