The Mechanism Of Receptor-like Kinase FERONIA In Regulating Plant Tolerance To Iron Deficiency

Iron(Fe)is the greatest essential microelement in plant growth and development,however,its bioavailability is often limited in well-aerated or calcareous soils.As a result,the plants in these soils are often suffered from iron deficiency and may even have decreased yield production.It is of great practical significance to elucidate the molecular and physiological mechanisms of how the plants tolerate to iron deficiency,so as to improve iron nutrition in crops by means of genetic breeding.Receptor-like kinase FERONIA plays multiple roles in plant abiotic stress response and yield control.However,the regulatory functions of this receptor-like kinase in iron nutrition are still unclear.Therefore,in this paper,we used Arabidopsis wild-type Col-0 and FERONIA-related mutants as the plant materials,and used plant physiology,molecular biology and other means to preliminarily study the roles of FERONIA in plant response to iron deficiency and its underlying mechanisms,the main results are as follows:FERONIA-null mutants fer-4 was less tolerant to iron deficiency than wild-type Col-0,which was characterized by severe chlorisis in leaves and can not re-green after long-term iron deficiency.And Fe levels in roots and shoots of fer-4 were also significantly lower than that of Col-0.The tolerance of iron deficiency as well as Fe levels could be recovered by complementation of FERONIA in the background fer-4.Overexpression of FERONIA in Col-0 background also improved the iron deficiency tolerance and Fe nutrition of plants.In addition,FER-GFP protein was found to be expressed in both roots and shoots of p FER::FER-GFP transgenic plants,and was significantly induced by iron deficiency.These results indicated that FERONIA positively regulated the tolerance to iron deficiency.Then,the difference in iron-deficiency responses between Col-0 and fer-4 was further studied.The results showed that iron deficiency significantly induced rhizosphere acidification of the wild type,but the opposite was true in fer-4.In addition,the activity of ferric reductase and the expression levels of FIT,IRT1 and FRO2 in fer-4 were all greatly lower than those in wild type under iron deficiency.Based on the above findings,FERONIA may improve plant tolerance to iron deficiency by inducing rhizosphere acidification,iron reductase activity as well as the expression of genes related to iron absorption.Given that fer-4 lost an ability of re-green after long-term iron deficiency.The roles of FERONIA in regulating Fe utilization in plants was then further investigated.Genome-wide analysis of gene expression affected by iron deficiency in Col-0 and fer-4 leaves revealed significant differences in the expression of genes related to cell wall synthesis or modification.Meanwhile,the apoplastic iron accumulation in the aboveground tissues of fer-4 was notably increased compared with that of Col-0.Further analysis showed that the loss of FERONIA function resulted in significantly improved iron retention in cell walls and increased de-esterified pectin content.These results suggest that induction of FERONIA under iron deficiency can improve iron utilization by reducing de-esterified pectin and iron fixation in the cell wall.In conclusion,FERONIA can improve plant tolerance to iron deficiency by positively regulating biological processes related to iron uptake in roots and utilization in shoots.Thus,the use of molecular breeding to enhance the activity of FERONIA homologs in crops could be expected to improve the iron nutrition,especially the iron use efficiency in shoots.