BOTRYTIS-INDUCED KINASE1, a plasma membrane-localized receptor-like protein kinase, is a negative regulator of phosphate homeostasis in Arabidopsis thaliana.

Huijuan Zhang,Fengming Song,Lei Huang,Yongbo Hong

doi:10.1186/s12870-016-0841-1

Abstract

BackgroundPlants have evolved complex coordinated regulatory networks to cope with deficiency of phosphate (Pi) in their growth environment; however, the detailed molecular mechanisms that regulate Pi sensing and signaling pathways are not fully understood yet. We report here that the involvement of Arabidopsis BIK1, a plasma membrane-localized receptor-like protein kinase that plays critical role in immunity, in Pi starvation response.ResultsqRT-PCR analysis revealed that expression of BIK1 was induced by Pi starvation and GUS staining indicated that the BIK1 promoter activity was detected in root, stem and leaf tissues of plants grown in Pi starvation condition, demonstrating that BIK1 is responsive to Pi starvation stress. The bik1 plants accumulated higher Pi content in root and leaf tissues and exhibited altered root architecture such as shorter primary roots, longer and more root hairs and lateral roots, as compared with those in the wild type plants, when grown under Pi sufficient and deficient conditions. Increased anthocyanin content and acid phosphatase activity, reduced accumulation of reactive oxygen species and downregulated expression of Pi starvation-induced genes including PHR1, WRKY75, AT4, PHT1;2 and PHT1;4 were observed in bik1 plants grown under Pi deficient condition. Furthermore, the expression of PHO2 was downregulated while the expression of miRNA399a and miRNA399d, which target to PHO2, was upregulated in bik1 plants, compared to the wild type plants, when grown under Pi deficient condition.ConclusionOur results demonstrate that BIK1 is a Pi starvation-responsive gene that functions as a negative regulator of Pi homeostasis in Arabidopsis.

Highlights

Plants have evolved complex coordinated regulatory networks to cope with deficiency of phosphate (Pi) in their growth environment; the detailed molecular mechanisms that regulate Pi deficiency (Pi) sensing and signaling pathways are not fully understood yet
Responsiveness of BOTRYTIS-INDUCED KINASE1 (BIK1) to Pi starvation When grown on MS medium under normal conditions, the bik1 plants produced shorter primary roots and longer and significantly more root hairs and lateral roots than wild type (WT) plants [68], which is reminiscent of the mutants with defects in Pi nutrition [75]
The transcript levels of BIK1 in seedlings grown under –Pi condition increased at 12 h and peaked at 24 and 48 h after transferring, leading to 7.5 ~ 11.2 folds of increases over those in seedlings grown under + Pi condition (Fig. 1a)

Summary

Introduction

Plants have evolved complex coordinated regulatory networks to cope with deficiency of phosphate (Pi) in their growth environment; the detailed molecular mechanisms that regulate Pi sensing and signaling pathways are not fully understood yet. To cope with Pi deficiency, plants develop a series of tightly controlled adaptive responses including external developmental alterations of. Physiological and biochemical studies in Arabidopsis have demonstrated that the acquisition, allocation, and metabolism of Pi are highly regulated processes and require the concerted action of multiple membrane Pi transport systems [19,20,21,22,23]. Most of the plasma membrane-localized high affinity transporters in the Pht family mediate Pi acquisition from external environment [1, 24, 28,29,30].

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