Functional analysis of MeCIPK23 and MeCBL1/9 in cassava defense response against <italic>Xanthomonas axonopodis</italic> pv. <italic>manihotis</italic>.

Key message: MeCIPK23 interacts with MeCBL1/9, and they confer improved defense response, providing potential genes for further genetic breeding in cassava.Abstract: Cassava (<italic>Manihot esculenta</italic>) is an important food crop in tropical area, but its production is largely affected by cassava bacterial blight. However, the information of defense-related genes in cassava is very limited. Calcium ions play essential roles in plant development and stress signaling pathways. Calcineurin B-like proteins (CBLs) and CBL-interacting protein kinases (CIPKs) are crucial components of calcium signals. In this study, systematic expression profile of 25<italic>MeCIPKs</italic> in response to <italic>Xanthomonas axonopodis</italic> pv. <italic>manihotis</italic> (<italic>Xam</italic>) infection was examined, by which seven candidate <italic>MeCIPKs</italic> were chosen for functional investigation. Through transient expression in <italic>Nicotiana benthamiana</italic> leaves, we found that six <italic>MeCIPKs</italic> (<italic>MeCIPK5, MeCIPK8, MeCIPK12, MeCIPK22, MeCIPK23</italic> and <italic>MeCIPK24</italic>) conferred improved defense response, via regulating the transcripts of several defense-related genes. Notably, we found that MeCIPK23 interacted with MeCBL1 and MeCBL9, and overexpression of these genes conferred improved defense response. On the contrary, virus-induced gene silencing of either MeCIPK23 or MeCBL1/9 or both genes resulted in disease sensitive in cassava. To our knowledge, this is the first study identifying MeCIPK23 as well as MeCBL1 and MeCBL9 that confer enhanced defense response against <italic>Xam</italic>. [ABSTRACT FROM AUTHOR]