Comparative transcriptome and physiological analyses reveal involvement of photosynthesis, phytohormone signaling, and cysteine-methionine metabolism in arsenic toxicity tolerance in Brassica napus.

This study investigates the physiological, biochemical, and molecular responses of two Brassica napus (B. napus) cultivars, ZD622 and ZD630, exposed to arsenic (As) stress. ZD630 was more resistant to As-induced toxicity, as demonstrated by higher biomass retention, less chlorophyll degradation, and less impairment of photosynthetic activity than ZD622. Photosynthetic parameters like as Pn and chlorophyll fluorescence were less influenced in ZD630, indicating a higher resilience in maintaining photosynthetic machinery integrity. Ultrastructural study demonstrated that ZD630 caused less damage to cellular components such thylakoid membranes and mitochondria. Moreover, ZD630 more efficient As exclusion mechanism, as seen by decreased arsenic accumulation in aerial tissues, led to its higher stress performance. Comparative transcriptome analysis was conducted to further dissect the molecular mechanisms underlying these morpho-physiological traits. KEGG pathway analysis revealed that the pathways for photosynthesis, auxin signaling, and amino acid metabolism were overrepresented suggesting these pathways may play important roles in the differential response to As between the two cultivars. ZD630 revealed activation of genes related to photosystem II repair, auxin transport, MAPK signaling, and ABA receptors, which might contribute to its improved stress response. Additionally, the differential control of cysteine and methionine metabolism contributes to ZD630 improved capacity to detoxify As via glutathione production.