Isolation and characterization of a spotted leaf 32 mutant with early leaf senescence and enhanced defense response in rice

Abstract

Leaf senescence is a complex biological process and defense responses play vital role for rice development, their molecular mechanisms, however, remain elusive in rice. We herein reported a rice mutant spotted leaf 32 (spl32) derived from a rice cultivar 9311 by radiation. The spl32 plants displayed early leaf senescence, identified by disintegration of chloroplasts as cellular evidence, dramatically decreased contents of chlorophyll, up-regulation of superoxide dismutase enzyme activity and malondialdehyde, as physiological characteristic, and both up-regulation of senescence-induced STAY GREEN gene and senescence-associated transcription factors, and down-regulation of photosynthesis-associated genes, as molecular indicators. Positional cloning revealed that SPL32 encodes a ferredoxin-dependent glutamate synthase (Fd-GOGAT). Compared to wild type, enzyme activity of GOGAT was significantly decreased, and free amino acid contents, particularly for glutamate and glutamine, were altered in spl32 leaves. Moreover, the mutant was subjected to uncontrolled oxidative stress due to over-produced reactive oxygen species and damaged scavenging pathways, in accordance with decreased photorespiration rate. Besides, the mutant showed higher resistance to Xanthomonas oryzae pv. Oryzae than its wild type, coupled with up-regulation of four pathogenesis-related marker genes. Taken together, our results highlight Fd-GOGAT is associated with the regulation of leaf senescence and defense responses in rice.

OsACL‐A2 negatively regulates cell death and disease resistance in rice

“…By far, a number of LMM genes have been identified to encode proteins with different functions, such as a Cullin domain protein (Liu et al ., ), eukaryotic translation elongation factor 1 alpha (eEF1A)‐like protein (Wang et al ., ), ferredoxin‐dependent glutamate synthase (Sun et al ., ), AAA‐type ATPase (Zhu et al ., ), putative MAPKKK (Wang et al ., ), UDP‐ N ‐acetylglucosamine pyrophosphorylase 1 (Wang et al ., ), splicing factor 3b subunit 3 (Chen et al ., ), a clathrin‐associated adaptor protein (Qiao et al ., ), and an E3 ubiquitin ligase (Zeng et al ., ). These findings indicate that numerous proteins are involved in the regulation of HR cell death and disease resistance.…”

Transcriptome Analysis of a Premature Leaf Senescence Mutant of Common Wheat (Triticum aestivum L.)

“…PYL9 and OsSPL32 are involved in the stress response. Overexpression of PYL9 can enhance drought resistance and accelerate leaf senescence [ 35 ], and mutation of OsSPL32 can enhance the defense response and induce leaf senescence in rice [ 36 ].…”

Knocking Out the Gene RLS1 Induces Hypersensitivity to Oxidative Stress and Premature Leaf Senescence in Rice

“…The most visible physiological change which takes place during leaf senescence is the gradual loss of chlorophyll [ 7 , 27 , 28 ]; this was also the case for the premature senescence experienced by rls1 ( Figure 6 A–C). The development of senescence in rls1 was accompanied by the up-regulation of SGR ( Figure 6 F); the product of this gene has been suggested to actively regulate chlorophyll degradation [ 9 ].…”

“…The notion that the heightened content of ROS in the leaf of the rls1 mutant is, at least in part, responsible for the premature leaf senescence syndrome and the heightened sensitivity to oxidative stress was consistent with the observation that H 2 O 2 exposure raised the leaf ROS content, thereby accelerating and exacerbating the syndrome ( Figure 5 and Figure 6 ). The tissue content of MDA, a product of membrane lipid peroxidation, is widely used as a marker for oxidative stress-induced cellular damage [ 27 , 32 ]. The rls1 mutant developed a significantly higher level of MDA in its leaves than did WT ( Figure 7 B).…”