The effect of CaNAC2csilencing on pepper growth,
thermotolerance and response to RSI
To assay the possible role of CaNAC2c in pepper response to HTS
or RSI, we assayed the effect of CaNAC2c silencing by VIGS on
response of pepper plants to HTS or RSI. The results showed thatCaNAC2c was successfully silenced by the two vectors (Figure 1A
and B). It was found that upon HTS, the CaNAC2c silenced plants
exhibited decreased basal and acquired thermotolerance, displayed with
serious wilt phenotype, high levels of plant mortality from 1 to 42 hpt
with or without pretreatment of
nonlethal
high temperature (Figure 1C and D). The
decreased thermotolerance was
accompanied with significant downregulation of thermotolerance relatedCaHSP24, CaHSFB2a and CaHSP70 (Ashraf et al., 2018)
(Figure1E-G).We also found that ion leakage upon HTS displayed by
conductivity in CaNAC2c silenced plants was significantly higher
than that of the control plants (Figure 1H and I). The DAB and NBT
staining representing H2O2 and ROS
accumulation, which were previously found to be negatively related to
thermotolerance(Yu et al., 2019; Zhuang et al., 2020), were much darker
in the leaves and stems of CaNAC2c -silenced plants than that in
the control plants (Figure 1J and K).We also foundCaNAC2c -silenced plants exhibited lower levels of Fv/Fm and
actual photochemical efficiency of PSII in the light (фPSII), indicator
of thermotolerance and thermostability of the photosynthetic apparatus,
respectively(Guan et al., 2018; Wang, Zhang, Goatley, & Ervin, 2014;
Yan et al., 2008), immediately after the HTS treatment(Figure 1L and M).
All these data indicate that CaNAC2c acts as positive regulator
in basal and acquired thermotolerance. By contrast, the CaNAC2csilenced pepper plants were inoculated with R. solanacearum , but
no difference was found between the CaNAC2c silenced and the
control plants (Data not shown). In addition, the CaNAC2csilenced pepper plants exhibited promotion not only in plant height and
size of roots, stems and leaves, but also in leaf and flower number
(Figure 2), indicating that CaNAC2c acts negatively in pepper growth and
development.