Glutamate synthase 1 is involved in iron-deficiency response and long-distance transportation in Arabidopsis

Iron is an essential microelement for plant growth.After uptake from the soil,iron is chelated by ligands and translocated from roots to shoots for sub-sequent utilization.However,the number of ligands in-volved in iron chelation is unclear.In this study,we identified and demonstrated that GLU1,which encodes a ferredoxin-dependent glutamate synthase,was involved in iron homeostasis.First,the expression of GLU1 was strongly induced by iron deficiency condition.Second,lesion of GLU1 results in reduced transcription of many iron-deficiency-responsive genes in roots and shoots.The mutant plants revealed a decreased iron concentration in the shoots,and displayed severe leaf chlorosis under the condition of Fe limitation,compared to wild-type.Third,the product of GLU1,glutamate,could chelate iron in vivo and promote iron transportation.Last,we also found that supplementation of glutamate in the medium can alleviate cadmium toxicity in plants.Overall,our results provide evidence that GLU1 is involved in iron homeo-stasis through affecting glutamate synthesis under iron deficiency conditions in Arabidopsis.

SKIP Confers Osmotic Tolerance during Salt Stress by Controlling Alternative Gene Splicing in Arabidopsis

Deciphering the mechanisms underlying plant responses to abiotic stress is key for improving plant stress resistance. Much is known about the regulation of gene expression in response to salt stress at the tran- scriptional level; however, little is known about this process at the posttranscriptional level. Recently, we demonstrated that SKIP is a component of spliceosome that interacts with clock gene pre-mRNAs and is essential for regulating their alternative splicing and mRNA maturation. In this study, we found that skip-1 plants are hypersensitive to both salt and osmotic stresses, and that SKIP is required for the alter- native splicing and mRNA maturation of several salt-tolerance genes, including NHXl, CBL1, P5CS1, RCl2A, and PATIO. A genome-wide analysis revealed that SKIP mediates the alternative splicing of many genes under salt-stress conditions, and that most of the alternative splicing events in skip-1 involve intron retention and can generate a premature termination codon in the transcribed mRNA. SKIP also controls alternative splicing by modulating the recognition or cleavage of 5＇ and 3＇ splice donor and acceptor sites under salt-stress conditions. Therefore, this study addresses the fundamental question of how the mRNA splicing machinery in plants contributes to salt-stress responses at the posttranscriptional level, and provides a link between alternative splicing and salt tolerance.