Silencing of the CaCP gene delays salt- and osmotic-induced leaf senescence in Capsicum annuum L.

Huai-Juan Xiao,Wei-Guo Chai,Yan-Xu Yin,Zhen-Hui Gong

doi:10.3390/ijms15058316

Abstract

Cysteine proteinases have been known to participate in developmental processes and in response to stress in plants. Our present research reported that a novel CP gene, CaCP, was involved in leaf senescence in pepper (Capsicum annuum L.). The full-length CaCP cDNA is comprised of 1316 bp, contains 1044 nucleotides in open reading frame (ORF), and encodes a 347 amino acid protein. The deduced protein belongs to the papain-like cysteine proteases (CPs) superfamily, containing a highly conserved ERFNIN motif, a GCNGG motif and a conserved catalytic triad. This protein localized to the vacuole of plant cells. Real-time quantitative PCR analysis revealed that the expression level of CaCP gene was dramatically higher in leaves and flowers than that in roots, stems and fruits. Moreover, CaCP transcripts were induced upon during leaf senescence. CaCP expression was upregulated by plant hormones, especially salicylic acid. CaCP was also significantly induced by abiotic and biotic stress treatments, including high salinity, mannitol and Phytophthora capsici. Loss of function of CaCP using the virus-induced gene-silencing technique in pepper plants led to enhanced tolerance to salt- and osmotic-induced stress. Taken together, these results suggest that CaCP is a senescence-associated gene, which is involved in developmental senescence and regulates salt- and osmotic-induced leaf senescence in pepper.

Highlights

Leaf senescence is the last stage of leaf development during which the nutrients deposited in leaves are remobilized to other developing organs of the plant [1,2]
A sequence of 662 bp was obtained from GenBank, which has high similarity to Nicotiana tabacum senescence-specific cysteine proteases (CPs) gene
A CP gene was identified from pepper

Summary

Introduction

Leaf senescence is the last stage of leaf development during which the nutrients deposited in leaves are remobilized to other developing organs of the plant [1,2]. Early leaf senescence resulting from diverse adverse environmental factors leads to the decline of photosynthetic activity, thereby restraining the accumulation of nutrients and limiting crop yield [3]. The cysteine proteases (CPs) with a cysteine residue at the active center have been extensively studied because they are involved in a variety of proteolytic functions in higher plants [6]. They are associated with many processes of plant development, including seed germination, leaf and flower development, fruit ripening, as well as in legume nodule development [7,8,9,10,11,12]. CsCP transcripts were enhanced during the development of citrus postharvest peel pitting and Asnodf encodes a nodule-specific CP in Astragalus sinicus [10,13]

Results

Discussion

Conclusion