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A parasite-infected host may promote performance of associated insect vectors; but possible parasite effects on nonvector insects have been largely unexplored. Here, we show that Begomovirus, the largest genus of plant viruses and transmitted exclusively by whitefly, reprogram plant immunity to promote the fitness of the vector and suppress performance of nonvector insects (i.e., cotton bollworm and aphid). Infected plants accumulated begomoviral βC1 proteins in the phloem where they were bound to the plant transcription factor WRKY20. This viral hijacking of WRKY20 spatiotemporally redeployed plant chemical immunity within the leaf and had the asymmetrical benefiting effects on the begomoviruses and its whitefly vectors while negatively affecting two nonvector competitors. This type of interaction between a parasite and two types of herbivores, i.e., vectors and nonvectors, occurs widely in various natural and agricultural ecosystems; thus, our results have broad implications for the ecological significance of parasite-vector-host tripartite interactions.

The effect of 24-epibrassinolide (EBR) on glucosinolate biosynthesis in Arabidopsis thaliana was investigated in the present study by using mutants and transgenic plants involved in brassinosteroid (BR) biosynthesis and signal transduction, as well as glucosinolate biosynthesis. The results showed that EBR significantly decreased the contents of major aliphatic glucosinolates including glucoiberin (S3), glucoraphanin (S4), and glucoerucin (T4), as well as the indolic glucosinolates glucobrassicin (IM) and neoglucobrassicin (1IM). In addition, a significantly higher level of glucosinolates accumulated in the BR-deficient mutant cpd and a dramatically lower glucosinolate content in the transgenic plant DWF4-ox overexpressing the BR biosynthetic gene DWF4 compared with their related wild-types, confirmed the repressing effect of BR on glucosinolate biosynthesis. BRI1, the receptor of BR signal transduction, was involved in regulation of glucosinolate biosynthesis by BR. Furthermore, the observation of reduced content of glucosinolates and lower expression levels of glucosinolate biosynthetic genes in 35S-BZR1/bzr1-1D and bes1-D plants compared with the corresponding wild-types suggested that BZR1 and BES1, two important components in BR signal transduction, are responsible for the inhibiting role of BR in glucosinolate biosynthesis. The disappearance of the repressing effect of BR on glucosinolate content in the myb28, myb34, and myb122 mutants indicated that these three MYB factors are important for the regulation of BR in glucosinolate biosynthesis.

The effects of industrial pre-freezing processing and freezing handling on the contents of glucosinolates and antioxidants (vitamin C, polyphenols, carotenoid and chlorophyll), as well as the antioxidant capacity in broccoli (Brassica oleracea L. var. italica) florets were investigated in the present study. Our results showed that the glucosinolate accumulations were significantly decreased after pre-freezing processing, whereas elevated levels of phenols, carotenoids, chlorophyll, and also antioxidant capacity were observed in frozen broccoli florets. The contents of vitamin C remained constant during above mentioned processing. In conclusion, the current industrial freezing processing method is a good practice for the preservation of main antioxidant nutrients in broccoli florets, although some improvements in pre-freezing processing, such as steam blanching and ice-water cooling, are needed to attenuate the decrease in glucosinolate content.

These authors contributed equally to this work. SUMMARYThe mycotoxin fumonisin B1 (FB1) causes the accumulation of reactive oxygen species (ROS) which then leads to programmed cell death (PCD) in Arabidopsis. In the process of studying FB1-induced biosynthesis of glucosinolates, we found that indole glucosinolate (IGS) is involved in attenuating FB1-induced PCD. Treatment with FB1 elevates the expression of genes related to the biosynthesis of camalexin and IGS. Mutants deficient in aliphatic glucosinolate (AGS) or camalexin biosynthesis display similar lesions to Col-0 upon FB1 infiltration; however, the cyp79B2 cyp79B3 double mutant, which lacks induction of both IGS and camalexin, displays more severe lesions. Based on the fact that the classic myrosinase b-thioglucoside glucohydrolase (TGG)-deficient double mutant tgg1 tgg2, rather than atypical myrosinase-deficient mutant pen2-2, is more sensitive to FB1 than Col-0, and the elevated expression of TGG1, but not of PEN2, correlates with the decrease in IGS, we conclude that TGG-dependent IGS hydrolysis is involved in FB1-induced PCD. Indole-3-acetonitrile (IAN) and indole-3-carbinol (I3C), the common derivatives of IGS, were used in feeding experiments, and this rescued the severe cell death phenotype, which is associated with reduced accumulation of ROS as well as increased activity of antioxidant enzymes and ROS-scavenging ability. Despite the involvement of indole-3-acetic acid (IAA) in restricting FB1-induced PCD, feeding of IAN and I3C attenuated FB1-induced PCD in the IAA receptor mutant tir1-1 just as in Col-0. Taken together, our results indicate that TGG-catalyzed breakdown products of IGS decrease the accumulation of ROS by their antioxidant behavior, and attenuate FB1 induced PCD in an IAA-independent way.

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Lead (Pb) pollution is a growing environment problem that continuously threatens the productivity of crops. To understand the molecular mechanisms of plant adaptation to Pb toxicity, we examined proteome changes in Arabidopsis seedlings following Pb treatment by SWATH-MS, a label-free quantitative proteomic platform. We identified and quantified the expression of 1719 proteins in water- and Pb-treated plants. Among them, 231 proteins showed significant abundance changes (151 elevated and 80 reduced) upon Pb exposure. Functional categorization revealed that most of the Pb-responsive proteins are involved in different metabolic processes. For example, down-regulation of photosynthesis and biosynthesis of isoprenoids and tetrapyrroles in chloroplasts were observed. On the contrary, pathways leading to glutathione, jasmonic acid (JA), glucosinolate (GSL), and phenylpropanoid production are up-regulated. Experimental characterizations demonstrated a rapid elevation of endogenic JA production in Pb-treated Arabidopsis seedlings, while a JA-deficient mutant and a JA-insensitive mutant showed hypersensitivity to root inhibition by Pb, implicating an essential role of JA during Pb responses. Consistently, methyl jasmonate supplementation alleviated Pb toxicity in the wild-type and JA-deficient mutant. Furthermore, GSL levels were substantially enhanced following Pb treatment, while such induction was not detected in the JA mutant, suggesting that the Pb-induced GSL accumulation is JA-dependent. Overall, our work represents the first SWATH-MS analysis in Arabidopsis and highlights a potential mediating role of JA during Pb stress.