AUTHOR=Xiao Xiaohu , Mo Chunyan , Sui Jinlei , Lin Xianzu , Long Xiangyu , Qin Yunxia , Fang Yongjun , Tang Chaorong 

TITLE=The Calcium Sensor Calcineurin B-Like Proteins -Calcineurin B-Like Interacting Protein Kinases Is Involved in Leaf Development and Stress Responses Related to Latex Flow in Hevea brasiliensis

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.743506

DOI=10.3389/fpls.2022.743506

ISSN=1664-462X

ABSTRACT=<p>Latex flow in <italic>Hevea brasiliensis</italic> (the Para rubber tree), the sole commercial source of natural rubber (<italic>cis</italic>-1,4-polyisoprene, NR), renders it uniquely suited for the study of plant stress responses. Calcineurin B-like interacting protein kinases (CIPK) serving as calcium-sensor protein kinases react with calcineurin B-like proteins (CBL) to play crucial roles in hormone signaling transduction and response to abiotic stress in plant developmental processes. However, little is known about their functions in <italic>Hevea</italic>. In this study, a total of twelve <italic>CBL</italic> (<italic>HbCBL</italic>) and thirty <italic>CIPK</italic> (<italic>HbCIPK</italic>) genes were identified from the <italic>Hevea</italic> genome. Structure and phylogenetic analysis assigned these CIPKs to five groups and CBLs to four groups, and mapped onto fourteen of the eighteen <italic>Hevea</italic> chromosomes. RNA-seq and qPCR analysis showed that the expressions of <italic>HbCBL</italic> and <italic>HbCIPK</italic> genes varied in the seven <italic>Hevea</italic> tissues examined, i.e., latex (cytoplasm of rubber-producing laticifers), bark, leaf, root, seed, female flower, and male flower. The expressions of two <italic>HbCBL</italic> and sixteen <italic>HbCIPK</italic> genes showed upward trends during leaf development. Following ethylene yield stimulation and the latex tapping treatment, both practices invoking stress, the expression levels of most latex-expressed genes were significantly altered. Yeast two-hybrid test revealed interactions for multiple combinations of HbCBLs and HbCIPKs with substantial gene expression in latex or other <italic>Hevea</italic> tissues. However, all the HbCBL-HbCIPK complexes examined did not recruit HbSOS1 or AtSOS1 to form functional salt tolerance SOS pathway in yeast cells. Taken together, the results suggested a role of the <italic>Hevea</italic> CBL-CIPK network as a point of convergence for several different signaling pathways in growth, development, and stress responses in relation to latex production.</p>