Plant hypersensitive response vs pathogen ingression: Death of few gives life to others

The hypersensitive response (HR) is a defense action against pathogen ingression. Typically, HR is predictable
with the appearance of the dead, brown cells along with visible lesions. Although death during HR can be limited
to the cells in direct contact with pathogens, yet cell death can also spread away from the infection site. The
variety in morphologies of plant cell death proposes involvement of different pathways for triggering HR. It is
considered that, despite the differences, HR in plants performs the resembling functions like that of animal
programmed cell death (PCD) for confining pathogen progression. HR, in fact, crucially initiates systemic signals
for activation of defense in distal plant parts that ultimately results in systemic acquired resistance (SAR).
Therefore, HR can be separated from other local immune actions/responses at the infection site. HR comprises of
serial events inclusive of transcriptional reprograming, Ca2+ influx, oxidative bursts and phyto-hormonal sig
naling. Although a lot of work has been done on HR in plants but many questions regarding mechanisms and
consequences of HRs remain unaddressed.We have summarized the mechanistic roles and cellular events of
plant cells during HR in defense regulation. Roles of different genes during HR have been discussed to clarify
genetic control of HR in plants. Generally existing ambiguities about HR and programmed cell death at the
reader level has been addressed