Identification of the Causative Genes of Calcium Deficiency Disorders in Horticulture Crops: A Systematic Review

Takanori Kuronuma,Hitoshi Watanabe

doi:10.3390/agriculture11100906

Abstract

The occurrence of calcium (Ca2+) deficiency disorders is a severe problem in the production of horticulture crops. Recently, several studies have investigated the role of gene expression in Ca2+ deficiency disorders and/or Ca2+ accumulation, providing an indication of the mechanism of Ca2+ deficiency disorders at the genetic level. To determine the relation between gene expression and the occurrence of Ca2+ deficiency disorders, we conducted a systematic review of the literature using the Preferred Reporting Items for Systematic Reviews and Meta-analyses protocol. In our initial search, we extracted studies investigating the relationships between Ca2+ deficiency disorders (tipburn and blossom-end rot) and gene expression. In our second search, we extracted studies involving functional analyses of the genes associated with Ca2+ deficiency and/or Ca2+ accumulation in plant organs. Thirty-seven articles were extracted from both searches. Studies on Ca2+ movement-related genes (Ca2+ antiporters, calreticulin, Ca2+ pumps, Ca2+ channels, and pectin methylesterases) accounted for the majority of these articles. Particularly, the effects of the expression of CAXs (Ca2+/H+ antiporters) and CRT (calreticulin) on the occurrence of Ca2+ deficiency disorders were demonstrated in studies extracted from both searches. Further research focusing on these genes may reveal the causative genes for Ca deficiency disorders in different horticulture crops. We hope that the knowledge synthesized in this systematic review will contribute to the accumulation of further knowledge and elucidation of the causes of Ca2+ deficiency disorders.

Highlights

Calcium (Ca2+) is an essential plant macronutrient, mainly transported via the xylem in the transpiration stream [1]
When we searched for studies that investigated the causative genes for Ca2+ deficiency disorders by conducting genetic analysis (Search 1), we focused only on two Ca2+ deficiency disorders, namely, tipburn and blossom-end rot (BER)
The sCAX1-expressing tomato was found to have accumulated excessive Ca2+ in the vacuole, and contained lower apoplastic and cytosolic Ca2+ concentrations than the wild-type did. These results clearly indicated that high expression of sCAX1 reduces the mobility of Ca2+, which leads to the development of BER in fruits

Summary

Introduction

Calcium (Ca2+) is an essential plant macronutrient, mainly transported via the xylem in the transpiration stream [1]. Its mobility from older plant organs to newly developed tissues is poor. Deficiency disorders is a serious concern in horticulture crop production because it causes significant economic losses [4,5,6]. Two Ca2+ deficiency disorders, tipburn and blossom-end rot (BER), have been studied since the 1800s, and it is becoming clearer how environmental conditions (e.g., humidity [7,8], light [5,9], and air flow [10,11]) can mitigate the damage caused by these disorders. No environmental control techniques to eliminate the occurrence of Ca2+ deficiency disorders have been found, and farmers instead often force the selection and production of cultivars with high resistance to Ca2+ deficiency disorders

Methods

Results

Conclusion