Rice EARLY SENESCENCE 2, encoding an inositol polyphosphate kinase, is involved in leaf senescence

Abstract

Background Early leaf senescence influences yield and yield quality by affecting plant growth and development. A series of leaf senescence-associated molecular mechanisms have been reported in rice. However, the complex genetic regulatory networks that control leaf senescence need to be elucidated. Results In this study, an early senescence 2 ( es2 ) mutant was obtained from ethyl methanesulfonate mutagenesis (EMS)-induced mutational library for the Japonica rice cultivar Wuyugeng 7 (WYG7). Leaves of es2 showed early senescence at the seedling stage and became severe at the tillering stage. The contents of reactive oxygen species (ROS) significantly increased, while chlorophyll content, photosynthetic rate, catalase (CAT) activity significantly decreased in the es2 mutant. Moreover, genes which related to senescence, ROS and chlorophyll degradation were up-regulated, while those associated with photosynthesis and chlorophyll synthesis were down-regulated in es2 mutant compared to WYG7. The ES2 gene, which encodes an inositol polyphosphate kinase (OsIPK2), was fine mapped to a 116.73-kb region on chromosome 2. DNA sequencing of ES2 in the mutant revealed a missense mutation, ES2 was localized to nucleus and plasma membrane of cells, and expressed in various tissues of rice. Complementation test and overexpression experiment confirmed that ES2 completely restored the normal phenotype, with chlorophyll contents and photosynthetic rate increased comparable with the wild type. These results reveal the new role of OsIPK2 in regulating leaf senescence in rice and therefore will provide additional genetic evidence on the molecular mechanisms controlling early leaf senescence. Conclusions The ES2 gene, encoding an inositol polyphosphate kinase localized in the nucleus and plasma membrane of cells, is essential for leaf senescence in rice. Further study of ES2 will facilitate the dissection of the genetic mechanisms underlying early leaf senescence and plant growth.

Genetic mapping and physiological analysis of chlorophyll-deficient mutant in Brassica napus L

“…There are more grana in the yellow-white leaf at advanced senescence compared with leaf for 6 days regreening [ 44 ]. In rice early senescence 2 (es2) mutant, more osmiophilic granules (OG) were found in es2 compared to wild type [ 45 ]. The SEM observations indicate that the mutant chloroplasts from young leaves might be in the senescence state.…”

Hexokinase gene OsHXK1 positively regulates leaf senescence in rice

“…A decrease in chlorophyll content is a significant characteristic of leaf senescence [ 35 ]. We measured the chlorophyll content of the WT, OsHXK1 -overexpressing, and OsHXK1 -CRISPR/Cas9 lines from the booting to the mature stage, and the results revealed a significant decrease in chlorophyll content in OsHXK1 -overexpressing leaves at the booting, flowering, and mature stages but an increase in the OsHXK1 -CRISPR/Cas9 lines compared with WT, consistent with the observed phenotypes in leaves (Fig.…”

Phytoplasma Infection Blocks Starch Breakdown and Triggers Chloroplast Degradation, Leading to Premature Leaf Senescence, Sucrose Reallocation, and Spatiotemporal Redistribution of Phytohormones

“…Impaired GA synthesis and metabolism are thought to be the cause of stunted growth. In addition, many early senescence mutants exhibited a retarded growth phenotype, with reduced plant height (dwarfism or semi-dwarfism), withered leaf tip, and decreased chlorophyll content [46]. In summary, leaf chlorosis, little leaf, and stunted growth are a series of consequences of premature leaf senescence caused by phytoplasma-induced sugar metabolism disorders.…”