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ZmbZIP60 mRNA is spliced in maize in response to ER stress.

Li Y, Humbert S, Howell SH - BMC Res Notes (2012)

Bottom Line: Splicing converts the predicted protein from a membrane-associated transcription factor to one that is targeted to the nucleus.Maize has numerous BIP-like genes, and ER stress was found to upregulate one of these, ZmBIPb.Among the genes upregulated by ER stress in maize is one of 22 BIP-like genes, ZmBIPb.

View Article: PubMed Central - HTML - PubMed

Affiliation: Plant Sciences Institute, Iowa State University, Ames, IA 50014, USA.

ABSTRACT

Background: Adverse environmental conditions produce ER stress and elicit the unfolded protein response (UPR) in plants. Plants are reported to have two "arms" of the ER stress signaling pathway-one arm involving membrane-bound transcription factors and the other involving a membrane-associated RNA splicing factor, IRE1. IRE1 in yeast to mammals recognizes a conserved twin loop structure in the target RNA.

Results: A segment of the mRNA encoding ZmbZIP60 in maize can be folded into a twin loop structure, and in response to ER stress this mRNA is spliced, excising a 20b intron. Splicing converts the predicted protein from a membrane-associated transcription factor to one that is targeted to the nucleus. Splicing of ZmbZIP60 can be elicited in maize seedlings by ER stress agents such as dithiothreitol (DTT) or tunicamycin (TM) or by heat treatment. Younger, rather than older seedlings display a more robust splicing response as do younger parts of leaf, along a developmental gradient in a leaf. The molecular signature of an ER stress response in plants includes the upregulation of Binding Protein (BIP) genes. Maize has numerous BIP-like genes, and ER stress was found to upregulate one of these, ZmBIPb.

Conclusions: The splicing of ZmbZIP60 mRNA is an indicator of ER stress in maize seedlings resulting from adverse environmental conditions such as heat stress. ZmbZIP60 mRNA splicing in maize leads predictively to the formation of active bZIP transcription factor targeted to the nucleus to upregulate stress response genes. Among the genes upregulated by ER stress in maize is one of 22 BIP-like genes, ZmBIPb.

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ZmbZIP60 splicing during maize development. (A) Maize seedlings of various ages were heat treated at 42°C for the indicated times. ZmbZIP60 mRNA splicing was analyzed as in Figure 2. (B) Following the heat stress of seedlings for 15 minutes, the splicing of ZmbZIP60 mRNA was observed in the basal (1), transitional (2), maturing (3), mature (4) regions of the third leaf [33]. (C) Leaves were detached from a seven-day-old seedling and incubated at RT or 42°C for the times indicated. (D) The tassel was detached from a mature maize plant and sprayed with DTT or subjected to heat treatment. RNA was extracted at various times after treatment and ZmbZIP60 mRNA splicing was detected using RT-PCR assays as described in Figure 2.
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Figure 5: ZmbZIP60 splicing during maize development. (A) Maize seedlings of various ages were heat treated at 42°C for the indicated times. ZmbZIP60 mRNA splicing was analyzed as in Figure 2. (B) Following the heat stress of seedlings for 15 minutes, the splicing of ZmbZIP60 mRNA was observed in the basal (1), transitional (2), maturing (3), mature (4) regions of the third leaf [33]. (C) Leaves were detached from a seven-day-old seedling and incubated at RT or 42°C for the times indicated. (D) The tassel was detached from a mature maize plant and sprayed with DTT or subjected to heat treatment. RNA was extracted at various times after treatment and ZmbZIP60 mRNA splicing was detected using RT-PCR assays as described in Figure 2.

Mentions: The stress responses examined thus far were observed in young (7-day old) seedlings. To determine whether they were dependent on developmental stage, older seedlings were heat treated and tested for ZmbZIP60 splicing. It was clear that the response was more robust in shoots of the 7-day-old seedlings compared to 2-week and 4-week old seedlings (Figure 5A). Taking advantage of the characteristics of monocot leaf growth, we also determined the efficiency of the splicing response at different stages of development within individual maize leaves. The maize leaf grows from its base towards the tip, creating a developmental gradient along the leaf axis. We subjected corn seedlings to a 15 min treatment at 42°C at the 3 leaf stage (about 10 day-old seedlings). The third leaves were excised and RNA was extracted from segments representing the basal (1), transitional (2), maturing (3) and mature (4) regions according to Li et al [33]. The youngest leaf regions, which included the basal and transitional regions, showed the most splicing activity (Figure 5B). Thus, the RNA splicing response to heat stress is more robust in younger seedlings than in older and in younger parts of the leaf than in older.


ZmbZIP60 mRNA is spliced in maize in response to ER stress.

Li Y, Humbert S, Howell SH - BMC Res Notes (2012)

ZmbZIP60 splicing during maize development. (A) Maize seedlings of various ages were heat treated at 42°C for the indicated times. ZmbZIP60 mRNA splicing was analyzed as in Figure 2. (B) Following the heat stress of seedlings for 15 minutes, the splicing of ZmbZIP60 mRNA was observed in the basal (1), transitional (2), maturing (3), mature (4) regions of the third leaf [33]. (C) Leaves were detached from a seven-day-old seedling and incubated at RT or 42°C for the times indicated. (D) The tassel was detached from a mature maize plant and sprayed with DTT or subjected to heat treatment. RNA was extracted at various times after treatment and ZmbZIP60 mRNA splicing was detected using RT-PCR assays as described in Figure 2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3369818&req=5

Figure 5: ZmbZIP60 splicing during maize development. (A) Maize seedlings of various ages were heat treated at 42°C for the indicated times. ZmbZIP60 mRNA splicing was analyzed as in Figure 2. (B) Following the heat stress of seedlings for 15 minutes, the splicing of ZmbZIP60 mRNA was observed in the basal (1), transitional (2), maturing (3), mature (4) regions of the third leaf [33]. (C) Leaves were detached from a seven-day-old seedling and incubated at RT or 42°C for the times indicated. (D) The tassel was detached from a mature maize plant and sprayed with DTT or subjected to heat treatment. RNA was extracted at various times after treatment and ZmbZIP60 mRNA splicing was detected using RT-PCR assays as described in Figure 2.
Mentions: The stress responses examined thus far were observed in young (7-day old) seedlings. To determine whether they were dependent on developmental stage, older seedlings were heat treated and tested for ZmbZIP60 splicing. It was clear that the response was more robust in shoots of the 7-day-old seedlings compared to 2-week and 4-week old seedlings (Figure 5A). Taking advantage of the characteristics of monocot leaf growth, we also determined the efficiency of the splicing response at different stages of development within individual maize leaves. The maize leaf grows from its base towards the tip, creating a developmental gradient along the leaf axis. We subjected corn seedlings to a 15 min treatment at 42°C at the 3 leaf stage (about 10 day-old seedlings). The third leaves were excised and RNA was extracted from segments representing the basal (1), transitional (2), maturing (3) and mature (4) regions according to Li et al [33]. The youngest leaf regions, which included the basal and transitional regions, showed the most splicing activity (Figure 5B). Thus, the RNA splicing response to heat stress is more robust in younger seedlings than in older and in younger parts of the leaf than in older.

Bottom Line: Splicing converts the predicted protein from a membrane-associated transcription factor to one that is targeted to the nucleus.Maize has numerous BIP-like genes, and ER stress was found to upregulate one of these, ZmBIPb.Among the genes upregulated by ER stress in maize is one of 22 BIP-like genes, ZmBIPb.

View Article: PubMed Central - HTML - PubMed

Affiliation: Plant Sciences Institute, Iowa State University, Ames, IA 50014, USA.

ABSTRACT

Background: Adverse environmental conditions produce ER stress and elicit the unfolded protein response (UPR) in plants. Plants are reported to have two "arms" of the ER stress signaling pathway-one arm involving membrane-bound transcription factors and the other involving a membrane-associated RNA splicing factor, IRE1. IRE1 in yeast to mammals recognizes a conserved twin loop structure in the target RNA.

Results: A segment of the mRNA encoding ZmbZIP60 in maize can be folded into a twin loop structure, and in response to ER stress this mRNA is spliced, excising a 20b intron. Splicing converts the predicted protein from a membrane-associated transcription factor to one that is targeted to the nucleus. Splicing of ZmbZIP60 can be elicited in maize seedlings by ER stress agents such as dithiothreitol (DTT) or tunicamycin (TM) or by heat treatment. Younger, rather than older seedlings display a more robust splicing response as do younger parts of leaf, along a developmental gradient in a leaf. The molecular signature of an ER stress response in plants includes the upregulation of Binding Protein (BIP) genes. Maize has numerous BIP-like genes, and ER stress was found to upregulate one of these, ZmBIPb.

Conclusions: The splicing of ZmbZIP60 mRNA is an indicator of ER stress in maize seedlings resulting from adverse environmental conditions such as heat stress. ZmbZIP60 mRNA splicing in maize leads predictively to the formation of active bZIP transcription factor targeted to the nucleus to upregulate stress response genes. Among the genes upregulated by ER stress in maize is one of 22 BIP-like genes, ZmBIPb.

Show MeSH
Related in: MedlinePlus