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Summary: Cassava is one of the most important tropical crops, but it is seriously affected by cassava bacteria blight (CBB) caused by the bacterial pathogen Xanthomonas phaseoli pv manihotis (Xam). So far, how pathogen Xam infects and how host cassava defends during pathogen–host interaction remains elusive, restricting the prevention and control of CBB.Here, the illustration of HEAT SHOCK PROTEIN 90 kDa (MeHSP90.9) interacting proteins in both cassava and bacterial pathogen revealed the dual roles of MeHSP90.9 in cassava–Xam interaction.On the one hand, calmodulin‐domain protein kinase 1 (MeCPK1) directly interacted with MeHSP90.9 to promote its protein phosphorylation at serine 175 residue. The protein phosphorylation of MeHSP90.9 improved the transcriptional activation of MeHSP90.9 clients (SHI‐RELATED SEQUENCE 1 (MeSRS1) and MeWRKY20) to the downstream target genes (avrPphB Susceptible 3 (MePBS3) and N‐aceylserotonin O‐methyltransferase 2 (MeASMT2)) and immune responses. On the other hand, Xanthomonas outer protein C2 (XopC2) physically associated with MeHSP90.9 to inhibit its interaction with MeCPK1 and the corresponding protein phosphorylation by MeCPK1, so as to repress host immune responses and promote bacterial pathogen infection.In summary, these results provide new insights into genetic improvement of cassava disease resistance and extend our understanding of cassava–bacterial pathogen interaction. [ABSTRACT FROM AUTHOR]

CPK1-mediated ERF72 protein phosphorylation confers improved disease resistance to cassava bacterial blight Keywords: cassava; ethylene response factor 72; protein phosphorylation; disease resistance; plant growth EN cassava ethylene response factor 72 protein phosphorylation disease resistance plant growth 2166 2168 3 10/19/23 20231101 NES 231101 Cassava provides food and income for about billion people worldwide (Maxmen, [4]). When Ser SP 40 sp residue was mutated into Ala (MeERF72 SP S40A sp ), no phosphorylation band could be examined in the phos-tag gel (Figure 1o), indicating that Ser SP 40 sp of MeERF72 was essential for its protein phosphorylation by MeCPK1. [Extracted from the article]

SUMMARY: Ethylene and melatonin are widely involved in plant development and environmental stress responses. However, the role of their direct relationship in the immune response and the underlying molecular mechanisms in plants remain elusive. Here, we found that Xanthomonas axonopodis pv. manihotis (Xam) infection increased endogenous ethylene levels, which positively modulated plant disease resistance through activating melatonin accumulation in cassava. In addition, the ethylene‐responsive transcription factor ETHYLENE INSENSITIVE LIKE5 (MeEIL5), a positive regulator of disease resistance, was essential for ethylene‐induced melatonin accumulation and disease resistance in cassava. Notably, the identification of heat stress transcription factor 20 (MeHsf20) as an interacting protein of MeEIL5 indicated the association between ethylene and melatonin in plant disease resistance. MeEIL5 physically interacted with MeHsf20 to promote the transcriptional activation of the gene encoding N‐acetylserotonin O‐methyltransferase 2 (MeASMT2), thereby improving melatonin accumulation. Moreover, MeEIL5 promoted the physical interaction of MeHsf20 and pathogen‐related gene 3 (MePR3), resulting in improved anti‐bacterial activity of MePR3. This study illustrates the dual roles of MeEIL5 in fine‐tuning MeHsf20‐mediated coordination of melatonin biosynthesis and anti‐bacterial activity, highlighting the ethylene‐responsive MeEIL5 as the integrator of ethylene and melatonin signals in the immune response in cassava. [ABSTRACT FROM AUTHOR]

SUMMARY: Heat shock protein 90 (HSP90) is involved in plant growth and various stress responses via regulating protein homeostasis. Autophagy keeps cellular homeostasis by recycling the components of cellular cytoplasmic constituents. Although they have similar effects on cellular protein homeostasis, the direct association between HSP90 and autophagy signaling remains unclear in plants, especially in tropical crops. In this study, the correlation between HSP90 and autophagy signaling was systematically analyzed by protein–protein interaction in cassava, one of the most important economy fruit in tropic. In addition, their effects on plant disease response and underlying mechanisms in cassava were investigated by functional genomics and genetic phenotype assay. The potential MeHSP90.9‐MeSGT1‐MeRAR1 chaperone complex interacts with MeATGs and subsequently triggers autophagy signaling, conferring improved disease resistance to cassava bacterial blight (CBB). On the contrary, HSP90 inhibitor and autophagy inhibitor decreased disease resistance against CBB in cassava, and autophagy may be involved in the potential MeHSP90.9‐MeSGT1‐MeRAR1 chaperone complex‐mediated multiple immune responses. This study highlights the precise modulation of autophagy signaling by potential MeHSP90.9‐MeSGT1‐MeRAR1 chaperone complex in autophagy‐mediated disease resistance to CBB. [ABSTRACT FROM AUTHOR]

Both autophagy and melatonin play important roles in plant development and stress response. However, the direct correlation between autophagy and melatonin as well as the underlying mechanism remains elusive in plants. In this study, we discovered that the expression of three autophagy‐associated genes (MeATG8b, 8c, and 8e) and autophagic activity were induced by exogenous melatonin treatment in cassava. In addition, three melatonin biosynthesis enzymes (tryptophan decarboxylase 2 (MeTDC2), N‐aceylserotonin O‐methyltransferase 2 (MeASMT2), and MeASMT3) positively regulate endogenous melatonin level and autophagic activity. Further investigation showed that these melatonin biosynthesis enzymes interacted with MeATG8b/8c/8e in vivo and in vitro. Consistently, MeTDC2, MeASMT2, and MeASMT3 also positively regulate endogenous melatonin level and autophagic activity in cassava. Notably, overexpression of MeATG8b, 8c, and 8e facilitated the protein expression level of MeTDC2, MeASMT2, and MeASMT3 in vivo. Taken together, melatonin synthesis enzymes (MeTDC2, MeASMT2/3) interact with MeATG8b/8c/8e and thus coordinate the dynamics of melatonin biosynthesis and autophagic activity in cassava, highlighting the links between melatonin biosynthesis and autophagic activity in cassava. [ABSTRACT FROM AUTHOR]