Abstract
Drought stress reduces water availability in plant cells and influences rapeseed yield. Currently, key genetic regulators that contribute to rapeseed response to drought remain largely unexplored, which limits breeding of drought-resistant rapeseed. In this study, we found that Brassica napus JASMONATE ZIM-DOMAIN 5 (BnA.JAZ5), one of the transcriptional repressors functioning in the jasmonate (JA) signaling pathway, was triggered by drought treatment in rapeseed, and drought-susceptibility increased in BnA.JAZ5-overexpressing rapeseed plants as compared to wild-type plants, resulting in a lower survival rate after recovery from dehydration. After recovery for 3 days, 22–40% of p35S::BnA.JAZ5 transgenic plants survived, while approximately 61% of wild-type plants survived. Additionally, seed germination of BnA.JAZ5-overexpressing rapeseed was hyposensitive to abscisic acid (ABA). The germination rate of five transgenic lines was 32~42% under 9 µM ABA treatment, while the germination rate of wild-type plants was 14%. We also found that the average stomatal density of five overexpressing lines was 371~446/mm2, which is higher than that of wild-type (232/mm2) plants under normal conditions. These results indicate that BnA.JAZ5 regulated drought response in an ABA-dependent manner, possibly by affecting stomatal density. Interestingly, methyl jasmonate (MeJA) treatment rescued the ABA-hyposensitive seed germination, revealing crosstalk between JAZ5-meidated JA and the ABA signaling pathway. Taken together, our results suggest that BnA.JAZ5 attenuated drought resistance through the ABA-dependent pathway, which could represent important genetic loci for drought-resistant rapeseed breeding.
Highlights
Various environmental stresses affect plant growth and yield
To investigate whether JAZ5 in rapeseed is involved in drought stress response, we checked the expression profiles of BnA.JAZ5 and BnC.JAZ5 in 18-day-old rapeseed treated with 20%
Rate showed no difference with the combination of abscisic acid (ABA) and JA treatment, suggesting that these results suggest that BnA.JAZ5 regulated rapeseed plant responses to drought stress
Summary
Various environmental stresses affect plant growth and yield. Water availability is the most important abiotic factor contributing to plant evolution [1]. Establishment of seedlings is directly inhibited by drought stress, which reduces plant densities and yields [2]. With the reduction in arable land worldwide, global food production needs to be increased to feed an ever-growing population [3]. Thereby, genetic engineering must be integrated with breeding technologies to develop climate-resilient crops adaptable to environmental changes leading to stress conditions. Rapeseed (Brassica napus, AACC, 2n = 36), as an important oilseed crop used for animal fodder and human consumption, is very sensitive to environmental stresses during its growth and reproductive stages [4,5]
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