Identification and Characterization of HAESA-Like Genes Involved in the Fruitlet Abscission in Litchi.

Fei Wang,Zhihui Zheng,Ye Yuan,Minglei Zhao,Jianguo Li

doi:10.3390/ijms20235945

Abstract

Regulation of abscission is an important agricultural concern since precocious abscission can reduce crop yield. INFLORESCENCE DEFICIENT IN ABSCISSION (IDA) peptide and its receptors the HAESA (HAE) and HAESA-like2 (HSL2) kinases have been revealed to be core components controlling floral organ abscission in the model plant Arabidopsis. However, it is still unclear whether the homologs of IDA-HAE/HSL2 in non-model plants are correlated to abscission. Previously, we found LcIDL1, a homolog of IDA from litchi, has a similar role to AtIDA in control of floral organ abscission in Arabidopsis. Here, we further isolated an HAESA-like homolog, LcHSL2, which is likely involved in the fruitlet abscission in litchi. Ectopic expression of LcHSL2 in wild type Arabidopsis has no effect on the floral organ abscission. However, its presence in the hae hsl2 mutant background completely rescued the floral organ abscission deficiency. LcHSL2 is localized in the cell membrane and the LcHSL2 gene is expressed at the pedicel abscission zone (AZ) of litchi and floral AZ of Arabidopsis. Real-time PCR analysis showed that the expression level of LcHSL2 was increased during ethephon-induced fruitlet abscission in litchi. Taken together, our findings suggest that HSL2 homologs have functional conservation in Arabidopsis and litchi, and LcHSL2 might play a critical role in regulation of fruitlet abscission in litchi.

Highlights

Abscission in general is an important process in plants to shed unwanted or infected organs in response to internal or external cues [1]
GmIDL2a and GmIDL4a, two homologs of IDA in soybean, could promote the cell separation during lateral root emergence through regulating the cell wall remodeling gene expression [28]. These findings suggest that the IDA-HAE/HSL2 signaling module can control cell separation events other than just floral organ abscission
We identified a homolog of IDA, LcIDL1, which is associated with the fruitlet abscission in litchi and has a similar function to Arabidopsis IDA in lateral root emergence through regulating the cell wall remodeling gene expression [28]

Summary

Introduction

Abscission in general is an important process in plants to shed unwanted or infected organs in response to internal or external cues [1]. The abscission process in plants takes place at the cell files in the specialized abscission zone (AZ) between the organ to be shed and the main plant body. The AZ will go through three sequential developmental stages when the abscission process is activated: (i) Acquisition of competence to respond to abscission signals; (ii) cell wall loosening and expansion followed by organ separation; and (iii) transdifferentiation of the retained portion of the AZ to generate a protective layer [2,3,4]. A core signaling pathway has been defined to regulate the floral organ abscission in model plant Arabidopsis [5,6,7,8,9]

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Results

Conclusion