The Persimmon 9-lipoxygenase Gene DkLOX3 Plays Positive Roles in Both Promoting Senescence and Enhancing Tolerance to Abiotic Stress

Abstract

The lipoxygenase (LOX) pathway is a key regulator for lipid peroxidation, which is crucial for plant senescence and defense pathways. In this study, the transcriptional expression patterns of three persimmon (Diospyros kaki L. ‘Fupingjianshi’) 9-lipoxygenase genes (DkLOX1, DkLOX3, and DkLOX4) were investigated. DkLOX1 was specifically expressed in fruit, particularly in young fruit, and showed little response to the postharvest environments. DkLOX4 was expressed in all tissues and slightly stimulated by mechanical damage and low temperature. DkLOX3 was expressed mainly in mature fruit, and the expression was extremely high throughout the storage period, apparently up-regulated by mechanical damage and high carbon dioxide treatments. Further functional analysis showed that overexpression of DkLOX3 in tomato (Solanum lycopersicum cv. Micro-Tom) accelerated fruit ripening and softening. This was accompanied by higher malondialdehyde (MDA) content and lycopene accumulation, advanced ethylene release peak and elevated expression of ethylene synthesis genes, including ACS2, ACO1, and ACO3. In addition, DkLOX3 overexpression promoted dark induced transgenic Arabidopsis leaf senescence with more chlorophyll loss, increased electrolyte leakage and MDA content. Furthermore, the functions of DkLOX3 in response to abiotic stresses, including osmotic stress, high salinity and drought were investigated. Arabidopsis DkLOX3 overexpression (DkLOX3-OX) transgenic lines were found to be more tolerant to osmotic stress with higher germination rate and root growth than wild-type. Moreover, DkLOX3-OX Arabidopsis plants also exhibited enhanced resistance to high salinity and drought, with similar decreased O2- and H2O2 accumulation and upregulation of stress-responsive genes expression, including RD22, RD29A, RD29B, and NCED3, except for FRY1, which plays a negative role in stress response. Overall, these results suggested that DkLOX3 plays positive roles both in promoting ripening and senescence through lipid peroxidation and accelerated ethylene production and in stress response via regulating reactive oxygen species accumulation and stress responsive genes expression.

Hydrogen sulfide regulates photosynthesis of tall fescue under low-light stress

“…It can be assumed that the accumulation of cytotoxic ROS subsequently caused lipid peroxidation, overproduction of MDA, and enzyme inactivation in chloroplasts, affecting carbon assimilation of photosynthesis (Li et al 2017). Moreover, excessive MDA might reflect that the apparatus of photosynthesis was damaged and the content of Chl was remarkably reduced (Hou et al 2015). In the current study, LL stress increased the MDA content, implying that the functionality and integrity of membranes were severely repressed, which was similar to the finding reported in cucumber (Zhang et al 2011).…”

DkXTH8, a novel xyloglucan endotransglucosylase/hydrolase in persimmon, alters cell wall structure and promotes leaf senescence and fruit postharvest softening

“…A. thaliana ecotype ‘Columbia’ was transformed via the floral dip method49, and T3 homozygous transgenic lines (AL1, AL2 and AL3) were generated. Cultivar Micro-Tom was transformed via Agrobacterium -mediated leaf transformation as described by Hou et al 28,. and T1 transgenic lines (TL1, TL2 and TL3) were used.…”

“…Persimmon ( Diospyros kaki L.) is not only an important economic crop but also displays evident changes in texture during ripening, making this species a good model for studying fruit softening2829. In our previous studies, seven XTH genes (DkXTH1–7) were amplified from persimmon, and these genes were proposed to be involved in fruit development, ripening or softening627.…”

Temperature Modulates Sex-Biased Gene Expression in the Gametophytes of the Kelp Saccharina latissima

“…(Lipinska et al, 2015) although female-specific in the first and male-specific in the latter species. Lipoxygenases are involved in lipid oxidation and play an important role in the biosynthesis of oxylipins -lipophilic mediators that have several physiological functions such as senescence, growth and development, tolerance to stress, and cell homeostasis (Hou et al, 2015;Maynard et al, 2018). In brown algae, they are involved in the defense response to pathogens and grazing (Cosse et al, 2009;Ritter et al, 2017) and their synthesis was induced under copper stress (Ritter et al, 2008).…”