Insights into the molecular mechanisms underlying responses of apple trees to abiotic stresses

Apple(Malus×domestica)is a popular temperate fruit crop worldwide.However,its growth,productivity,and quality are often adversely affected by abiotic stresses such as drought,extreme temperature,and high salinity.Due to the long juvenile phase and highly heterozygous genome,the conventional breeding approaches for stress-tolerant cultivars are time-consuming and resource-intensive.These issues may be resolved by feasible molecular breeding techniques for apples,such as gene editing and marker-assisted selection.Therefore,it is necessary to acquire a more comprehensive comprehension of the molecular mechanisms underpinning apples’response to abiotic stress.In this review,we summarize the latest research progress in the molecular response of apples to abiotic stressors,including the gene expression regulation,protein modifications,and epigenetic modifications.We also provide updates on new approaches for improving apple abiotic stress tolerance,while discussing current challenges and future perspectives for apple molecular breeding.

Interfering small ubiquitin modifiers(SUMO)improves the thermotolerance of apple by facilitating the activity of MdDREB2A

Heat stress,which is caused by global warming,threatens crops yield and quality across the world.As a kind of post-translation modification,SUMOylation involves in plants heat stress response with a rapid and wide pattern.Here,we identified small ubiquitin modifiers(SUMO),which affect drought tolerance in apple,also participated in thermotolerance.Six isoforms of SUMOs located on six chromosomes in apple genome,and all the SUMOs were up-regulated in response to heat stress condition.The MdSUMO2 RNAi transgenic apple plants exhibited higher survival rate,lower ion leakage,higher catalase(CAT)activity,and Malondialdehyde(MDA)content under heat stress.MdDREB2A,the substrate of MdSUMO2 in apple,was accumulated in MdSUMO2 RNAi transgenic plants than the wild type GL-3 at the protein level in response to heat stress treatment.Further,the inhibited SUMOylation level of MdDREB2A in MdSUMO2 RNAi plants might repress its ubiquitination,too.The accumulated MdDREB2A in MdSUMO2 RNAi plants further induced heat-responsive genes expression to strengthen plants thermotolerance,including MdHSFA3,MdHSP26.5,MdHSP18.2,MdHSP70,MdCYP18-1 and MdTLP1.In summary,these findings illustrate that interfering small ubiquitin modifiers(SUMO)in apple improves plants thermotolerance,partly by facilitating the stability and activity of MdDREB2A.

Water quality induced corrosion of stainless steel valves during long-term service in a reverse osmosis system

The current study analyzes the contribution of 10 water quality parameters(including pH,turbidity,conductivity,total dissolved solids(TDS),hardness,total organic carbon(TOC),alkalinity,calcium ions,chlorides and sulfates) to corrosion extent of stainless steel valves taken from different locations in a reverse osmosis system of a reclaimed water plant.The valves were in service for 5 years.Raman spectroscopy and X-ray photoelectron spectroscopy analyses are conducted to quantify corrosion products on different valves under various water quality conditions.On that basis,bivariate and multivariate regression analyses between the 10 water quality parameters and the corrosion extent of valve specimens(represented by metal loss percentage(MLP) values) are carried out to check the contribution of those water quality parameters to MLP.The results indicate that the proportions of metal oxides as corrosion products vary according to the corrosion extent of the valves.Although no linear correlation is founds all 10 water quality parameters except for pH show a significant positive correlation with the MLP values of the valve specimens.Moreover,results of multivariate regression suggest that the variation of MLP can be explained by turbidity,TDS,TOC and sulfates.A positive contribution of turbidity,TDS and TOC to MLP is observed,whereas the contribution of sulfates is negative.The results from the current work help to identify the reasons for water quality-induced failure of stainless steel equipment in RO systems.

APPLE SUMO E3 REGULATES LIGASE MDSIZ1 NEGATIVELY DROUGHT TOLERANCE

Drought stress typically causes heavy losses in apple production and uncovering the mechanisms by which apple tolerates drought stress is important in apple breeding.MdSIZl is a SUMO(small ubiquitin-like modifier)E3 ligase that promotes SUMO binding to substrate proteins.Here,we demonstrate that MdSIZl in apple has a negative relationship with drought tolerance.MdSIZ1 RNAi transgenic apple trees had a higher survival rate after drought stress.During drought stress they had higher leaf water potential,reduced ion leakage,lower H_(2)O_(2)and malondialdehyde contents,and higher catalase activity.In addition,MdSIZl RNAi transgenic plants had a higher net photosynthetic rate during the latter period of drought stress.Finally,the transgenic apple trees also altered expression levels of some microRNAs in response to drought stress.Taken together,these results indicate that apple MdSIZl negatively regulates drought stress by enhancing leaf water-holding capacity and antioxidant enzyme activity.

APPLE SUMO E3 LIGASE MDSIZ1 NEGATIVELY REGULATES DROUGHT TOLERANCE

General Introduction Frontiers of Agricultural Science and Engineering(FASE)is an authoritative source for professionals with interests encompassing agricultural science and engineering,supervised by the Chinese Academy of Engineering,administered by Higher Education Press of China and China Agricultural University,and published by Higher Education Press of China on a quarterly basis in English.