The Papain-like Cysteine Protease HpXBCP3 from Haematococcus pluvialis Involved in the Regulation of Growth, Salt Stress Tolerance and Chlorophyll Synthesis in Microalgae

Abstract

The papain-like cysteine proteases (PLCPs), the most important group of cysteine proteases, have been reported to participate in the regulation of growth, senescence, and abiotic stresses in plants. However, the functions of PLCPs and their roles in stress response in microalgae was rarely reported. The responses to different abiotic stresses in Haematococcus pluvialis were often observed, including growth regulation and astaxanthin accumulation. In this study, the cDNA of HpXBCP3 containing 1515 bp open reading frame (ORF) was firstly cloned from H. pluvialis by RT-PCR. The analysis of protein domains and molecular evolution showed that HpXBCP3 was closely related to AtXBCP3 from Arabidopsis. The expression pattern analysis revealed that it significantly responds to NaCl stress in H. pluvialis. Subsequently, transformants expressing HpXBCP3 in Chlamydomonas reinhardtii were obtained and subjected to transcriptomic analysis. Results showed that HpXBCP3 might affect the cell cycle regulation and DNA replication in transgenic Chlamydomonas, resulting in abnormal growth of transformants. Moreover, the expression of HpXBCP3 might increase the sensitivity to NaCl stress by regulating ubiquitin and the expression of WD40 proteins in microalgae. Furthermore, the expression of HpXBCP3 might improve chlorophyll content by up-regulating the expression of NADH-dependent glutamate synthases in C. reinhardtii. This study indicated for the first time that HpXBCP3 was involved in the regulation of cell growth, salt stress response, and chlorophyll synthesis in microalgae. Results in this study might enrich the understanding of PLCPs in microalgae and provide a novel perspective for studying the mechanism of environmental stress responses in H. pluvialis.

Salinity tolerance and desalination properties of a Haematococcus lacustris strain from eastern Hungary

“…The dynamics of the process, as well as the salt concentration at which the individual morphological changes occur, show a great variety between the different strains. The loss of flagella was reported already after 24 h with 0.1% (~1,000 mg l −1 ) and 86 mM (~5,000 mg l −1 ) NaCl ( Cordero et al, 1996 ; Liu et al, 2021 ). The appearance of the red pigment content was observed after 1–2 days ( Gao et al, 2015 ), the majority of cells transformed into red aplanospores in 3–5 days ( Zharova et al, 2022 ).…”

“…Most of the literature demonstrated that motile cells lose their flagella with increasing salinity, pigment accumulation occurs in the emerging non-motile cells ( Boussiba and Vonshak, 1991 ; Cordero et al, 1996 ; Gao et al, 2015 ; Liu et al, 2021 ; Zharova et al, 2022 ). The dynamics of the process, as well as the salt concentration at which the individual morphological changes occur, show a great variety between the different strains.…”

A Novel Senescence-Specific Gene (ZmSAG39) Negatively Regulates Darkness and Drought Responses in Maize

“…Papain-like cysteine proteases (PLCPs), one of the most abundant subfamilies of cysteine proteases, have nucleophilic cysteine thiols in their active sites and have been reported to be involved in the regulation of plant growth, senescence and abiotic stress [9]. At present, the cysteine protease gene family is generally divided into nine subfamilies, RD21, CEP, XCP, XBCP3, THI, SAG12, RD19, ALP and CTB9 [10].…”

“…HpXBCP3 was involved in the regulation of cell growth, salt stress response and chlorophyll synthesis in microalgae. This may be due to the strict control of protease activity to avoid sudden protein degradation [9].…”