Jasmonate signaling and remodeling of cell wall metabolism induced by boron deficiency in pea shoots

Boron (B) is an essential element for plant growth but its cellular functions are poorly defined. We conducted transcriptome analysis of shoot apices of pea (Pisum sativum L.) growing for up to 18 days in the presence or absence of borate. Shoots of B deficient plants exhibited impaired elongation of the apex but increased growth of lateral shoots. Transcriptome analysis at days 10, 14 and 18 revealed 42, 517 and 2684 differentially expressed genes (DEGs), respectively, relating to diverse aspects of cell growth, metabolism, membrane function and cell signaling. Genes involved in jasmonate signaling and cell wall metabolism were upregulated in the B deficient plants. Many DEGs encoded transcription factors (TFs) potentially involved in these responses including many MYB and ethylene-responsive transcription factor (ERF) proteins and two orthologs of MYC2 which has been implicated in jasmonate signaling. Treatment of detached apices with B or jasmonic acid (JA) led to rapid changes in the expression of several of these DEGs. These results are consistent with a major role for borate in cell wall structure, perturbation of which can activate jasmonate signaling and cell wall remodeling. Such changes can help to explain how B deficiency leads to changes in shoot growth and architecture.