The jasmonate-free rice mutant hebiba is affected in the response of phyA′/phyA″ pools and protochlorophyllide biosynthesis to far-red light

Abstract

Phytochrome (phy) A in its two native isoforms (phyA' and phyA") and the active (Pchlide(655)) and inactive (Pchlide(633)) protochlorophyllides were investigated by low-temperature fluorescence spectroscopy in the tips of rice (Oryza sativa L. Japonica cv Nihonmasari) coleoptiles from wild type (WT) and the jasmonate-deficient mutant hebiba. The seedlings were either grown in the dark or under pulsed (FRp) or continuous (FRc) far-red light (lambda(a) >/= 720 nm) of equal fluences. In the dark, the mutant had a long mesocotyl and a short coleoptile, whereas the situation was reversed under FR: short mesocotyl and long coleoptile, suggesting that the effect is mediated by phyA. Under these conditions the WT displayed a short coleoptile and emergence of the first leaf. In the dark, the spectroscopic and photochemical properties of phyA, its content and the proportion of its two pools, phyA' and phyA", were virtually identical between WT and hebiba. However, the total content of protochlorophyllides was higher in the mutant. Upon illumination with FRc, [phyA] declined in the WT and the ratio between phyA' and phyA" shifted towards phyA". In hebiba, the light-induced decline of [phyA] was less pronounced and the ratio between phyA' and phyA" did not shift. Moreover, in the WT, FRp stimulated the biosynthesis of Pchlide(655), whereas FRc was inhibiting. In contrast, in the mutant, both FRp and FRc stimulated the synthesis of Pchlide(655). This means that FRc caused the opposite effect in hebiba. This difference correlates with a slower photodestruction of primarily the light-labile phyA' pool in hebiba.

Jasmonate and Phytochrome A Signaling inArabidopsisWound and Shade Responses Are Integrated through JAZ1 Stability

“…Turner, unpublished data). The hebiba mutant seedlings also have higher levels of active protochlorophyllide than their wild-type counterparts in the dark and in FR (Sineshchekov et al, 2004). This indicates that JA signaling regulates chlorophyll biosynthesis during skotomorphogenesis and during photomorphogenesis in FR-enriched light, in both monocots and dicots.…”

“…Crucially, integration of the JA and phyA signal pathways was at the level of JAZ1 stability: phyA was required for JAZ1 destabilization by wounding or exogenous JA. The photodestruction of phyA is in part controlled by JA, as was demonstrated in the hebiba mutant of rice (Sineshchekov et al, 2004;Riemann et al, 2009). Together, our results establish that the control of protein stability is central to the integration of these two signal pathways.…”

“…Significantly, hebiba is male sterile, compromised in JA accumulation, and has been reported to map close to a known JA biosynthesis gene. The light-regulated turnover of the phyA protein is delayed in hebiba and restored by exogenous JA, suggesting a specific role for JA in a key facet of phytochrome A signaling (Sineshchekov et al, 2004;Riemann et al, 2009). In addition, a knockout mutation in the rice homolog of JAR1 is insensitive to FR and blue light inhibition of coleoptile elongation (Riemann, et al, 2008).…”

Pseudomonas fluorescens WCS374r-Induced Systemic Resistance in Rice against Magnaporthe oryzae Is Based on Pseudobactin-Mediated Priming for a Salicylic Acid-Repressible Multifaceted Defense Response

“…] with BTH, indicating that SA accumulation is not a prerequisite for the expression of BTH-inducible blast resistance. To investigate whether JA and/or ET play a role in WCS374r-mediated ISR, we tested the effectiveness of WCS374r in the ET-insensitive OsEIN2-suppressed transgenic line 471 (Jun et al, 2004) and the JA-deficient mutant hebiba, which is impaired in an as yet unidentified step of the octadecadoid pathway (Riemann et al, 2003;Sineshchekov et al, 2004). In contrast to the respective wild-type lines Dongyin and Nihonmasari, both 471 and hebiba were blocked in their ability to develop WCS374r-mediated ISR, whereas chemical induction of blast resistance by BTH resulted in levels of induced resistance comparable to those observed in the wild type.…”

A Critical Role for the TIFY Motif in Repression of Jasmonate Signaling by a Stabilized Splice Variant of the JASMONATE ZIM-Domain Protein JAZ10 inArabidopsis

“…JA is well known for its ability to promote plant defense responses against insect herbivores, necrotrophic pathogens, and various abiotic stresses as well (Pozo et al, 2004;Glazebrook, 2005;Browse and Howe, 2008;Howe and Jander, 2008). JA also plays an important role in normal plant growth and development, including cell division, cell fate determination, photomorphogenesis, and sexual reproduction (McConn and Browse, 1996;Li et al, 2004;Sineshchekov et al, 2004;Browse, 2005;Chen et al, 2007;Balbi and Devoto, 2008). An important attribute of JA is its ability to act both as a potent inhibitor of vegetative growth and as a positive regulator of reproductive and defensive processes (Yan et al, 2007;Howe and Jander, 2008;Mitra and Baldwin, 2008;Pauwels et al, 2008).…”