Enhanced Cytokinin Synthesis in Tobacco Plants Expressing PSARK::IPT Prevents the Degradation of Photosynthetic Protein Complexes During Drought

Abstract

To identify genes associated with the cytokinin-induced enhanced drought tolerance, we analyzed the transcriptome of wild-type and transgenic tobacco (Nicotiana tabacum 'SR1') plants expressing P(SARK)::IPT (for senescence-associated receptor kinase::isopentenyltransferase) grown under well-watered and prolonged water deficit conditions using the tomato GeneChip. During water deficit, the expression of genes encoding components of the carotenoid pathway leading to ABA biosynthesis was enhanced in the wild-type plants, but repressed in the transgenic plants. On the other hand, transgenic plants displayed higher transcript abundance of genes involved in the brassinosteroid biosynthetic pathways. Several genes coding for proteins associated with Chl synthesis, light reactions, the Calvin-Benson cycle and photorespiration were induced in the transgenic plants. Notably, increased transcript abundance of genes associated with PSII, the cytochrome b(6)/f complex, PSI, NADH oxidoreductase and the ATP complex was found in the P(SARK)::IPT plants. The increased transcript abundance was assessed by quantitative PCR and the increased protein levels were confirmed by Western blots. Our results indicated that while the photosynthetic apparatus in the wild-type plants was degraded, photosynthesis in the transgenic plants was not affected and photosynthetic proteins were not degraded. During water deficit, wild-type plants displayed a significant reduction in electron transfer and photochemical quenching, with a marked increase in non-photochemical quenching, suggesting a decrease in energy transfer to the PSII core complexes and an increase in cyclic electron transfer reactions.

Salicylic acid application modulates physiological and hormonal changes in Eucalyptus globulus under water deficit

“…These compounds possess ideal structural abiotic stress (Pospíšilová et al, 2000). It has been described that 523 CKs play an important role in the development of the plant 524 photosynthetic apparatus by directly affecting the chloroplast and 525 reducing chlorophyll degradation (Rivero et al, 2010). In fact, 526 according Dwivedi et al (2014) Other works also showed that through PGR exogenous application 599 not only plant physiology is altered but also the general hormone 600 status of the plant (Meijón et al, 2011a …”

Stress-Induced Cytokinin Synthesis Increases Drought Tolerance through the Coordinated Regulation of Carbon and Nitrogen Assimilation in Rice

“…Other hormones, in particular CK, salicylic acid, ethylene, and jasmonic acid, also play direct or indirect roles in the plant responses to abiotic stress . Under drought stress, plant CK content decreases, and the reduction in CK increases the plant responses to increasing ABA (Davies and Zhang, 1991), inducing stomata closure and inhibiting photosynthesis (Rivero et al, 2010). Our previous results suggested that the stress-induced CK synthesis, driven by a stress-induced promoter, protected against the deleterious effects of water deficit on the photosynthetic apparatus, allowing higher photosynthetic rates and higher yields after water deficit in tobacco (Rivero et al, 2009) and cotton (Gossypium hirsutum; Kuppu et al, 2013) plants grown in the greenhouse and peanut (Arachis hypogaea) plants grown under field conditions (Qin et al, 2011).…”

Conditional up-regulation of cytokinin status increases growth and survival of sugarcane in water-limited conditions

“…Similar results were also reported in IPT transgenic cotton (Kuppu et al, 2013), peanut (Qin et al, 2011) and tobacco (Rivero et al, 2010) with reduced water supply.…”