Field Crop 2024, Vol.7, No.6, 287-297 http://cropscipublisher.com/index.php/fc 288 2 Environmental Stresses Affecting Kiwifruit 2.1 Abiotic stresses Drought stress is a significant abiotic factor that affects kiwifruit growth and productivity. The R1R2R3-MYB transcription factor AcMYB3R has been identified as a key player in enhancing drought tolerance in kiwifruit. Overexpression of AcMYB3R in Arabidopsis thaliana has shown to upregulate stress-responsive genes such as RD29A, RD29B, COR15A, and RD22, leading to improved drought resistance (Zhang et al., 2019). Cold stress, including chilling injury, poses a major challenge for kiwifruit storage and quality. The bZIP transcription factor AchnABF1 has been found to enhance cold tolerance by upregulating genes associated with ABA-dependent and ABA-independent pathways, as well as improving ROS-scavenging abilities (Jin et al., 2021). Additionally, the bZIP transcription factor AcePosF21 regulates ascorbic acid biosynthesis, which helps mitigate oxidative damage caused by cold stress (Liu et al., 2023). Heat stress can adversely affect kiwifruit by disrupting cellular homeostasis and metabolic processes. Although specific studies on heat stress in kiwifruit are limited, the general stress-responsive mechanisms involving transcription factors like AcMYB3R, which also respond to heat stress, suggest potential pathways for enhancing heat tolerance (Zhang et al., 2019). Salt stress is another critical abiotic factor that impacts kiwifruit. The AcMYB3R transcription factor has been shown to enhance salt tolerance by upregulating stress-responsive genes in transgenic Arabidopsis thaliana, indicating its potential role in improving salt stress resistance in kiwifruit (Figure 1) (Zhang et al., 2019). Figure 1 Overexpression of AcMYB3Rresults in enhanced drought or salt tolerance (Adopted from Zhang et al., 2019) Image caption: A and B, phenotypes and the root length of wild type (WT) andAcMYB3R-overexpressing lines (#3, #5 and #6) under mimic drought stress on 0.5× MS medium. C, phenotype of WT and AcMYB3R-overexpressing lines (#3, #5 and #6) before and after drought stress treatments in pots. D and E, phenotypes and the root length of WT andAcMYB3R-overexpressing lines (#3, #5 and #6) under salt stress on 0.5× MS medium. F, phenotype of WT and AcMYB3R-overexpressing lines (#3, #5 and #6) before and after NaCl treatment in pots. Data in Fig. 4-B and E are mean±SD from three independent experiment. **, significant differences at P<0.01 by Student’s t-test (Adopted from Zhang et al., 2019)
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