A Rice Gene Homologous to Arabidopsis AGD2-LIKE DEFENSE1 Participates in Disease Resistance Response against Infection with Magnaporthe oryzae

Abstract

ALD1 (ABERRANT GROWTH AND DEATH2 [AGD2]-LIKE DEFENSE1) is one of the key defense regulators in Arabidopsis thaliana and Nicotiana benthamiana. In these model plants, ALD1 is responsible for triggering basal defense response and systemic resistance against bacterial infection. As well ALD1 is involved in the production of pipecolic acid and an unidentified compound(s) for systemic resistance and priming syndrome, respectively. These previous studies proposed that ALD1 is a potential candidate for developing genetically modified (GM) plants that may be resistant to pathogen infection. Here we introduce a role of ALD1-LIKE gene of Oryza sativa, named as OsALD1, during plant immunity. OsALD1 mRNA was strongly transcribed in the infected leaves of rice plants by Magnaporthe oryzae, the rice blast fungus. OsALD1 proteins predominantly localized at the chloroplast in the plant cells. GM rice plants over-expressing OsALD1 were resistant to the fungal infection. The stable expression of OsALD1 also triggered strong mRNA expression of PATHOGENESIS-RELATED PROTEIN1 genes in the leaves of rice plants during infection. Taken together, we conclude that OsALD1 plays a role in disease resistance response of rice against the infection with rice blast fungus.

Biochemical Principles and Functional Aspects of Pipecolic Acid Biosynthesis in Plant Immunity

“…Exogenously applied Pip also increases the resistance of tobacco plants to P. syringae pv tabaci infection and primes tobacco for early SA accumulation (VogelAdghough et al, 2013). Furthermore, transgenic rice plants overexpressing the Pip biosynthesis gene ALD1 exhibited increased resistance toward infection by the fungus Magnaporthe oryzae (Jung et al, 2016). Together, these findings suggest a conserved regulatory role for Pip in plant immunity.…”

“…Alkaline conditions have been proposed to favor enamine formation (Nardini et al, 1988). Subcellular localization studies in Arabidopsis and rice show that ALD1 fusion proteins localize to chloroplasts (Cecchini et al, 2015;Jung et al, 2016), indicating that the site of ALD1 action is the organelle in which the substrate L-Lys is biosynthesized (Mazelis et al, 1976). With pH values around 7 and 8 in the stroma of dark-exposed and illuminated chloroplasts, respectively (Werdan et al, 1975), the site of ALD1-mediated L-Lys conversion is neutral to moderately alkaline, which might favor the formation of the 2,3-DP enamine.…”

l‐lysine metabolism to N‐hydroxypipecolic acid: an integral immune‐activating pathway in plants

“…Further, the application of Pip also induced resistance of tobacco plants to infection by P. syringae and tobacco mosaic virus (Vogel‐Adghough et al ., ; Ádám et al ., ). In addition, overexpression of a rice homolog of Arabidopsis ALD1 in transgenic rice plants increased immunity to the rice blast fungus M. oryzae (Jung et al ., ). Therefore, the Pip/NHP resistance pathway is conserved between species belonging to very different angiosperm orders and, typical for its involvement in SAR, is active against (hemi)biotrophic pathogens with inherently different modes of plant infection (Sticher et al ., ).…”

“…In the following years, Pip was unequivocally identified as a natural product in leaves of Trifolium repens (white clover), in the pods of Phaseolus vulgaris (green bean), in young Malus domestica (apple) fruits and in several other plant species (Hulme and Arthington, ; Zacharius et al ., , ; Morrison, ; Broquist, ). Evidence for the presence of a pathway for biosynthesis of Pip in plants has since been presented for a rapidly growing list of monocot and dicot species, including the model crucifer Arabidopsis (Návarová et al ., ) and economically and nutritionally important crops such as potato ( Solanum tuberosum ; Zacharius et al ., ; Pálfi and Dészi, ), soybean ( Glycine max ; Aliferis et al ., ), barley ( Hordeum vulgare ; Møller, ), maize ( Zea mays ; Kiyota et al ., ), rice ( Oryza sativa ; Pálfi and Dészi, ; Jung et al ., ), and wheat ( Triticum sp. ; Garcia‐Seco et al ., ).…”

“…Bioassays in the context of the induction of flowering in Lemna and SAR in Arabidopsis (see below) demonstrate that the l ‐ but not the d ‐enantiomer of Pip is bioactive in plants (Fujioka et al ., ; Návarová et al ., ), strongly suggesting that plants biosynthesize l ‐Pip. Subcellular localization studies in Arabidopsis or rice with ALD1 and SARD4 proteins fused to reporter sequences indicate that biosynthesis of l ‐Pip proceeds in plastids (Sharma et al ., ; Cecchini et al ., ; Jung et al ., ), in which the precursor amino acid l ‐lysine is also synthesized (Mazelis et al ., ).…”